While I understand the idea in general Tux, the penguin, is basically freely available, do whatever you want with it, and you are explicitly encouraged to integrate the design into Linux related projects… as long as you mention the author should someone ask (source)

I wouldn’t even buy a pre-fabricated sticker but do one myself. But that wasn’t the question…

PS: the Impressum here or here, down at the bottom labeled “Impressum”?