welp, it's the danger with offering your artwork out for free.
a while ago i posted a free vector of a turntable on vecteezy. it became pretty popular and i'm glad about that....but! i don't think it's at all cool to download said vector, apply it to a tshirt, and sell it as your own design on a different design site (redbubble). if you're gonna do that, at least give me props.
have a look at 'my' design, which ain't so free anymore.