Unity lost any good will they built by changing their pricing to per install and making go into effect retroactively. Indie developers especially are up in arms.
Unity changed the license, so developers have to pay a fee for every install of games made with Unity. Notice that it's "install". Not "sale". Not "download".
They claim they won't count installs from demos, cracks, charity bundles, re-installs, etc, but absolutely no one trusts them at this point. Several devs have said they're switching engine, despite the large cost of that.
In the sense that it applies to games already released, but not to previous installs. Allegedly. One of the main problems with all of this is that detecting only "valid" installs is a very hard problem, if not impossible. Unity's attitude seems to be that devs just have to trust their numbers.
Additionally, some devs are reporting that they've been offered a pass on all this bs, if they switch to Unity's own ad platform.