I don't think we need to make a study of it to be sure that GitHub and Sourceforge are rife with free software ("free" in terms of beer, and in libre, and also in compensation) in various states of incompletion, haphazard execution, and sheer abandonment.
I mean: The open-source community has certainly produced a ton of excellent software for free, but it has also produced (and published) a lot of false starts, loose ends, broken or forgotten code, and unfinished or unpolished work.
Open-source volunteerism is awesome, but it isn't all ponies and rainbows.
Perhaps the author(s) of some of these things might care more about finishing and maintaining them if their ongoing efforts were producing a meaningful amount of money as a reward.