Are there any? I remember that I gave away a not-yet-released game some time ago and it bugged out and I had to contact support about the matter.

I'd really not want to do that again, so is it safe to hold a giveaway with a pre-order game? I was thinking of making one with Witcher 3...

Spill 'em all and let gog sort 'em out?

Well, thanks to a generous donation, some are already doing so: http://www.gog.com/forum/general/the_bizarrely_bonza_bonanza_bazaar_of_bazookery_giveaway_7/post2

Ah, I see. That is one major giveaway ,so it seems that I shouldn't hold my own then :D

Thanks for the info!

nah - hold your own if you want. the TBBBBOB is merely made up of donations.
I'm sure you could come up with something more creative / difficult to win! :)

You just get a code as any other, and it redeems like any other game.