[Solmu]

Some places in similiar veins - such as Threadless, I think? - have more restrictions.

Threadless aren't particularly similar (since they're not a fulfillment service), but yes - in submitting to Threadless you agree to give them exclusive right of first refusal to print the design. This used to last indefinitely (i.e. until you asked them to release the design, or they printed it), but that may not still be the case (I haven't looked lately).

 

[Solmu]

I seem to recall that the rights are yours again, if not selected, after 3 months.

I heard that too. It didn't used to be the case, but I suspect they may have changed their policy to something more reasonable.

(it would be easy enough to check... if I cared to )