As is pointed here the links for the locker app are broken
Does the f-droid servers hold a copy of the repo clone to make it available?
Edit: yes they do https://f-droid.org/repository/browse/?fdid=net.zygotelabs.locker
I installed this app today and it works perfectly. I wanted to propose some improvements
What does f-droid do in this situations? keep the app until it does not work in recent android versions?