This seems like a really bad idea to me. You can't charge for something that the user can just build themselves for free. Someone else is just going to distribute the binaries. And so what do you do about your repos, are those just for paying customers as well? You wind up with 2 Ubuntus in this scenario, both weaker than the 1 today.
> You can't charge for something that the user can just >build themselves for free.
Um, sure you can. Ubuntu, RedHat, and Slackware are quite successful at this already. Pat Volkerding has been doing it for as long as linux has existed (Slackware). Yes, someone can distribute the binaries, but they can't use the {Ubuntu, RedHat,Slackware} name.