I doubt the lack of license was the reason DJB's projects didn't take over the world. Most of them required heavy forking to break away from hardwired assumptions about the filesystem and play nice with the OS distribution, and DJB is himself notoriously difficult to work with. Still, qmail managed to establish maildir as the standard format and kill off mbox, and for that alone I'm eternally grateful.
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.