Paid features in opensource apps

Given the lack of FOSS email clients for android (except for K9, which does not see much development lately), I wanted to give Fair Email a try.

This is an email client app which appeared recently on fdroid and claims to be 100% open source and GPL compliant.

But, after installing it, I was quite disappointed when I discovered that some of the features require unlocking through a payment to the developer.

I am not sure that this is, legally speaking, against the license. If the “pro” features are in the source code, one could get it, disable the licence check and recompile it, or even fork it and publish fully free version of the app.

But I cannot hide my disappointment in seeing such “pay-to-unlock” fuss in a self proclaimed FOSS app. Just imagine if the same applied to linux kernel: pay to unlock a kernel module, or recompile it yourself if you have time and will…

What do you think about this topic? Is there any fdroid policy about this?

Making money is never against FLOSS or F-Droid principles.
Even if the paid for features themselves wouldn’t be FLOSS that would just mean the app gets marked with some kind of “promotes non free whatever” anti-feature.


K9 is constantly developed, what do you mean?

Developers need to eat too, strange, right?

It is not…

Be sure to include the source code, change the app name, be licence compliant and such , but yes…everyone can do that…

The app is Open source, you have free access to the source code, fdroid tools are free, Android Studio is free… WHAT DO YOU WANT MORE?

There is no topic, except your misplaced outrage


@Licaon_Kter Sorry for what you understood as “misplaced outrage”, but it was not intended to be anything like it.

I am used to use fora as places of discussion and confrontation, where one can share thoughts without being attacked.

If this forum has other rules, and unpolitely attacking those who dare to suggest something that might be interpreted as contrasting with someone else’s opinion is normal, then this is not my place.

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People sometimes say “free as in freedom, not as in free beer”. There is nothing wrong if someone tries to make money from free software. Notice that there are many apps on F-Droid with some kind of donation link. The author of Fair Email tries something else, which might seem unusual but is perfectly fine.

My interpretation why you feel attacked: you say, you are suggesting something contrasting with someone else opinion. The point is, as I view it, this topic is not about opinions (which are very welcome). People who care about free software have lots of different opinions about almost everything, but they will agree on one thing: Everyone has the freedom to do anything with the code as long as they observe the license. That’s what happened here. My guess is, that the strong word “misplaced” was chosen to make this clear.

If you read carefully my first message, you will see that while saying that I was “disappointed” by something that is not very common in the opensource community (i.e. license checking code built into the binary), I was just asking others what do they think about this. In fact, I was not even stating my position, but asking others for theirs. I think there was absolutely no reason for rude, unpolite and even SCREAMING answers, nor for tagging someone else’s post as “misplaced outrage”.

That said, I well know the difference between free beer and freedom, and never presumed that it is immoral to make money out of free software. Fortunately, there are a lot of developers doing that in many ways, and I appreciate and encourage them.

However I am not sure that a free/pro scheme is useful for the community. If all features, including “pro” ones, are included in the source, then you’re right, it’s perfectly legal, but in my opinion a bit pointless: one can just fork a clone app removing the restrictions.

If the “pro” features, instead, are not in the published source code (making them closed source), legality is guaranteed as long as the original copyright holder is the only developer. As soon as he/she starts to include community contributions (which are covered by the same license of the opensource version but not automatically included in the copyright of the main developer) in the opensource version, one should start to worry about the legality of building such contributed code into the paid version.

Again, these thoughts started from installing a specific app, but are not meant to question this specific app or its author directly. As the title says, it’s just a hint for a discussion on such schemes.


My message was meant to sound harsh, you could have limited yourself to the initial question “is it ok?” Where the answer is “Yes”, but noooo you had to start ranting and bringing the morality of the dev into question and other stuff.

You’re missing the point, THERE IS NO COMMUNITY, none so ever, nada, zip, nil, null…

Just one guy coding an app, offering it for free, fixing bugs and adding features in >1100 commits, answering >1600 posts on XDA. And no, those 9 PRs (where I have 3 onliners) don’t matter at all.

There is no “scheme”, you keep wording it sounding not in a “I’ve only asked a question” naive way as you say you meant in the first question, but rather with an undertone.

Yes, do fork the app, add a better colour scheme (I hate grey on white/black as much as anyone), then start fixing bugs, answering questions, adding features…for free…see how long can you go doing it for free, really I wonder how long it will take you until you realize that your time, mind, life is NOT for free after all?

Your first post comes as really disrespectful to someone who put a lot of time in FairEmail but also in NetGuard (the first app that I recommend to anyone on Android), just because you want those 2 useless features and you’re too lazy to compile it but not enough to post here.

And don’t get me wrong, while Marcel is above all that you’ve posted, I’ll keep him on check when he is wrong.

BTW, ungrateful users lead to LESS apps: not more :frowning:


@Licaon_Kter The only disrespectful thing here is your rage and disproportionate reaction to my hints for discussion.

I am not interested in losing more time discussing with someone with an ego so big that cannot tolerate a civil and polite confrontation.

Enjoy. Bye.


So, back to the facts.

FairEmail depends on a remote non-free network service to enable pro features through a challenge/reply mechanism (see based on a hashed version of the device id.

Code to reproduce this network service is obviously not available (although trivial to reproduce) and the server address is hardcoded.

Shouldn’t this qualify the app for “Non-free Network Service” anti-feature?


Shouldn’t this qualify the app for “Non-free Network Service” anti-feature?

Yes and no, but I agree that this is a worthy topic.

Hope others can lend an opinion.

Many people understand “free software” to be non-commercial. In English, that’s especially easy to do given the meanings of the word “free”. Sounds like @JackA had that understanding. I’m happy that they brought up the topic.

Free Software as defined by the Free Software Foundation or GPL/Apache/etc does not say anything regarding commercial or not. It is about whether people have the freedom to do anything they want with the source code. Selling binaries is compatible with Free Software. Paid-to-unlock features is also compatible with Free Software.

My opinion is that F-Droid should follow that understanding of Free Software, and not have any particular policy regarding commercial activity. I also think that F-Droid should promote donating to developers, and make it as easy and obvious as possible.


It looks like FairEmail is fully usable without the pro features, so that would be overkill.

Maybe we could say that it promotes non-free networking services, as I’m pretty sure the payment interface isn’t FOSS. Anyone?

I’m kind of sad to see people adding pro features like this, but I don’t see a problem yet. The author is just exploring ways to get some money for their time, as they have a right to, and hopefully so they can spend more time working on the app. If every app starts doing this, we might want to think about creating a new Anti-Feature for it.

I would be concerned if the app downloads binary executables to enable those pro features. Does it do that?

And even then, that would be accepted in F-Droid, be it with an antifeature, and we have several downloaders/updaters for non-free apps in the main repository.

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Not that I know, it should just generate a code and with that code and after a payment you get another code that unlocks those app features:

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@hans I fully understand the meaning of free software. I probably know long before many users on this forum.

But the point is not my understading. I am quite sure that such code, which locks some parts of the binary and unlocks only upon giving away id information and connecting to a non free network server (simple as it is, but still non free in the sense that you cannot substitute it), would not make its way in any reputable linux distribution. Or at least it would be patched out before being built. Just name a single package in Debian using this shareware-like (back to the 80’…) mechanism and I’ll concede.

I never said the point is to save a few Euros. I am happy to contribute if I a find some piece of software useful, and I am not saying that there is something wrong in the app itself, although I don’t personally think such mechanism is useful for the author himself (but that’s just my opinion, so anyone is free to disagree).

But the fact is that, as of now, a user of f-droid gets no information on some non-trivial facts on this app before installing it:

  • a part of the functionality is locked (a small part, someone says, but who decides how small is small enough?)
  • this part of the code depends a non free network service (very simple, but still, who decides how simple is simple enough)
  • the app gives away id data upon pressing the buy button without prior warning (the android id, even hashed, still remains a unique tracking id)
  • the app contains advertising (of itself, but still ad)

Of note, the app itself does not connect to anything except your mail, it just opens a web browser to his site with the challenge code.

Hence, maybe NonFreeAdd could be warranted, but not NonFreeNet

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Just because something is free software doesn’t mean it is not allowed to follow other principles too.
Apparently the Debian project has some additional principles, that doesn’t mean other free software projects have to follow them.

Perhaps not. F-Droid has its own rules, and the app meets our inclusion policy.

Additionally, F-Droid requires a cooperative upstream and would never patch out something against upstreams wishes. Upstream has to be notified and agree to inclusion before an app can even be included.

That said, anyone is free to fork the app, unlock the pro features by default, and ask for it to be included in F-Droid. (Edit: Thus becoming the direct upstream of this fork.)


This app seems to me that it has the anti-feature “advertising”.

Ultimately I feel we should add an antifeature for “pay-to-unlock”. While I fully support the developers’ right to include such things, I feel that many users will see a “pay money to make software work” as worse than including a few ads which we already mark as an “anti-feature”.


(I hope this adds to the conversation and does not distract. )
IMO we should explain to potential users what it means when we say that F-Droid apps are open source. The “os” part of Foss is of upmost importance to me and what compels me to be a supporter. (I am Free to “make” my own version from the source code but I can’t. -humor- I’m not a coder.) Asking me to buy additional functionality presents no problem. I’ve spent hundreds on Play store apps. [I’ve even uninstalled F-Droid apps and bought developer’s apps from the PS as a show of support. One example is NetGuard]

I believed two apps, on fdroid, couldn’t have the same name, could they ?