One business model that I’m surprised hasn’t been further explored for funding free software is advertising. Ads have been a standard way to make “free” media pay in countries like the USA, where advertising-based commercial television broadcasting has been the dominant medium for decades.
In the Debian project they refer to packages that no longer have mantainers as orphaned. I think it's a good definition, and I'd extend it to free software packages that are no longer developed.
There are a lot of orphaned packages around, some actually deserve it but unfortunately there are also some that are promising or very good, and now they are almost dead. But, since we are talking about free software, every good developer is encouraged to pick one and try to push it a bit further
Every software developer faces a choice when deciding how to release a new software product. That choice is whether the program will be free or non-free. Unfortunately, many otherwise knowledgeable programmers aren’t sure just what this choice means, and may complain that programmers with families really don’t have a choice at all—if they want to earn a living, they must charge for their work. However, free software is not about giving software away without cost.