ECB seems to have a free (libre) license; though it’s none officially “blessed” by OSI/FSF it seems to cover the basic “4 freedoms”. And to add to your line of thought: The toggle wouldn’t help avoiding NonFreeNet if the app won’t work with it toggled off (“entirely depends”)
Sure? Who has the precise definition for that when it comes to data? As pointed out: to me it looks like the “4 freedoms” are granted, which makes it libre. Others might come to different conclusions (see my notes on their 4th term that for commercial use one must not put data into frames – but that does not forbid commercial use, does it?). IMHO we should not demand the color of the dot on the “i” here.
I’d say then the users are free to choose and to set up their own “free API” – as long that’s not just a “nice theory” as there’s no way to feed it, it should be fine.
The AntiFeature text says that’s the solution even
This antifeature would not apply, if there is a simple configuration option that allows pointing the app to a running instance of an alternative, publicly available, self-hostable, free software server solution.