Hi Steve,
I may be completely wrong, but I believe MPEG Streamclip is based on QuickTime and the Apple MPEG 2 CODEC and without these, the program doesn’t even work. The MPEG CODEC is a part of Final Cut, but without it I think you have to buy it from Apple for $20.
I’m guessing that since you buy it from Apple or get it bundled with FCP, that royalties are in fact being paid. I’m not sure how it works with Avid though.
Anyways, hope that helps you out a little.
Rey