> By taking over stewardship of something that people depend on you should have some obligation

No. If it's free and open source, all it says is what you can do with the code. There is no obligation towards the users whatsoever.

If you choose to depend on something, it's your problem. The professional way to do it is either to contractually make sure that the project doesn't "fuck you over" (using your words), or to make sure that you are able to fork the project if necessary.

If you base your business on the fact that someone will be working for you, for free, forever, then it's your problem.