We typically call Drizzle a fork, since we do have a common ancestor at this point (though it is doubtful you could apply a patch between the two). We are pretty up front about this though. Drizzle is supported by Sun which the article does not mention, though we are different in that we have patches that have to date come in from 30+ companies.
OurSQL is more of a distribution then anything else. Their tree is a collection of patches they apply at each release.