> the optimal solution is for the masses benefitting from the library to return some of that benefit (perhaps in monetary form) to the author. But culturally this is not what free-software is about...

There's been quite a bit of improvement in that problem space. Crowd-sourcing is now considered by users a natural way to fund new work. So much so that in more user facing apps users are constantly asking about it if you don't have a campaign already. There are also micro-transaction solutions like gratipay (previously gittip) that are more open-ended and continuous which probably works better for lower layer projects and when developers don't want to fiddle with managing crowd-sourcing campaigns. Github could very easily own that space if they implemented something like "give x$ per month to every project I've starred".