Though not the sort of question you’ll have to think too hard about, unless you’re one of the utter, utter cretins this is being written to address. I’m going to nudge you ever so gently in the direction of the right answer, because I’m a sport like that. Look at this picture:

Done? Take your time, these words will still be here when you’re ready. What is this picture? Is it:
a) Michael Schumacher testing a GP2 car, in a test which has been sanctioned by the FIA, the F1 testing committee and GP2, which allows GP2 to gain feedback on their new car and a big old dollop of publicity while also giving Michael’s troublesome neck a workout?
b) That cheating German git getting in some practice before the F1 testing ban ends on February 1st?
Still not sure? It’s a). Now leave.
The limits placed on off-season testing in F1 were designed as a money saving measure. They don’t exist to keep drivers out of racing cars, though that inevitably happens. If a driver wishes to do something else over the winter to keep his hand in, and the necessary permissions are given, he can do so.
In this case, Michael Schumacher is doing it because it’s in everyone’s interests to have a race-fit Schumi in Bahrain on March 14th, because there are few better ways of drawing attention to your new car than getting the most successful F1 driver in history to break it in, and because it’s the kind of thing you do when the only thing you know is how to win.
Um… what about the GP3 that’s (theoretically?) making it’s debut this year?
Funny you should mention that. The first GP3 test was carried out by Mark Webber, who as far as I’m aware remains an F1 driver. Remarkably little uproar there, or indeed when Felipe Massa tested a 2008 Ferrari F1 car today in Barcelona as part of his own comeback…
See, I want to see the GP3s hit the tarmac. They’re pretty frickin’ sexy. ^_^