Well, there were always plenty of patches available - it's just that lots of them conflicted with each other, and that was a product of the licensing.
Agreed with the rest, though. I relied heavily on qmail for about a decade, and learned a lot from the experience, even if it was a little terrifying on occasion!
These days one would just most likely create a fork on github. Vim was also maintained through separate patches for a long time, but Bram was a lot more accepting about integrating and distributing those patches himself.