What is MB's involvement with Red Bull?

On the home page of autosport, they have a small section on the right with tabs GP, Video, Magazine and Ferrari. I just watched the current video titled 'Brawn to sell to Mercedes' in which they say that MB will likely take a 75% share in the team. Fine, we already know something like that is probably in the works.

Toward the end, they mention they're also involved with McLaren how the MB name is part of the team title, McLaren-Mercedes. The narrator goes on to say "despite having a large share in Red Bull, Mercedes aren't allowed to be in the official team name. This is due to the terms of their contract with McLaren." Is this true, and if so for how long has it been the case? I just can't believe it considering which engines power the RB cars.

And maybe I missed it here from a few weeks ago, but I just found this on f1live:

It's quite an interesting situation if MB does indeed have a share in Red Bull, that McLaren has such veto powers (apart from spreading their seed across F1).