Right. Specifically, it's the intersection of a public domain license and a program that gets a lot of commercial use (esp. embedded in devices). I know of some

Right. Specifically, it's the intersection of a public domain license and a program that gets a lot of commercial use (esp. embedded in devices). I know of some other public domain programs (off the top of my head: several of lhf's libraries for Lua), but nothing else that has had the license carefully scrutinized for commercial use.