Slashdot | Software For Ransom
This is an interesting idea. I wasn't able to read anything in-depth because the stupid pages were all slashdotted.
In any case, I think with short time spans and reasonable amounts of money, this could work well. One problem I couls forsee is a small group of users constantly paying for the entire group's usage, however it would be those people who would be most likely to use the application and it's source code to the fullest.