They are participating - which is completely valid as long as they pay the test fee. That is not the same as "endorsing." Just because those companies participate has nothing to do with the AV labs scamming anyone.
VBulletin and AV-Test are not scam labs. They perform a certain set of tests, with a certain methodology, for a fee. It's paid testing.
Lots of things being said about AV test labs, lots of it baseless and ridiculous. Everyone runs their mouth on forums, yet no one steps forward and disproves the test methodology... which, I might add, is an exercise in futility. The labs don't always get it right. However, it takes someone with experience such as Fabian Wosar to point the issues out.