I think Linux's model is the strongest: individual contributors retain copyright, and there are enough individual copyright holders to make relicensing insanely difficult. Coupled with the project's pace (and the pace at which they change the internal APIs) it basically provides such a guarantee. Most projects however are less successful and the users/downstream developers can't count on momentum as the safeguard.
Not unless they retroactively change the license on said previous work, which I'm pretty sure they cannot.
Currently owned by Opera since 2021.
It's why some folks are still using Photoshop CS6.
I bought game maker studio version 1 for mobile and paid a great deal of money for it, it was shortly before they released the new version of 2.0 with the new model and then android dropped support for 32 bit mobile applications. I was unable to build my android apps moving forward because 1.0 never supported 64bit while 2.0 did.
It took me a bit to finally come around to using the engine again (I currently pay the monthly fee as I develop my game)