> they have paid programmers who write stuff for Ubuntu,
> which the other distributions also use.

I've been thinking your statement in question ("Ubuntu makes their money out of server services, and a lot of popular distros are made out of that codebase, by paid developers.") was saying who makes Ubuntu-based distros, not who makes Ubuntu (= "that codebase"). If not, I've apparently misunderstood the meaning of that sentence.