Some signal that the project is being maintained? If it’s not that’s fine but don’t go radio silent and get pissy when people ask if a project is dead…
This is not a legal or moral issue it’s just being considerate for others as well. You, the maintainer, made the choice to maintain this project in the public and foster a userbase. This is not a one-way relationship. People spend their time making patches and integrating your software. You are under no obligation to maintain it of course but dont be a dick.
The implication is the mistake, not the author for not being explicit enough.
Further, what makes you assume everyone is on the same page about what that social contract is? Have you even considered the possibility that there might be differences of opinion on a social contract which are incompatible? It's why the best course of action is to follow the license rather than delusional fantasies.
The idea there's a social contract is sophistry. Plain and simple.
This is a pretty bold and loud acknowledgement.
What more could you really ask for when even lawyers think this is sufficient.