At first, I upovted zepolen's comment about there being no social contract, only license, but something bugged me about that, and I felt that I wasn't right.

After thinking about it for a while, I think that you are right, there is an implicit social contract when using open source software, and a part of this contract would be to expect the maintaining people to provide the best quality software they can create.

But the thing about contracts is that they work between multiple parties, and not just the maintainer(s) and some void. And consumers of the library didn't do their due diligence, that is, supporting the code that they rely on.