Just making sure you know about our June game art contest.
Please read the full announcement and join us in the official forums.
Are we free to use the above art commercially?
@cloud_magic: basically yes but you need to take a very close look at the GPL3 and CC-BY-SA 3.0 licenses.
The gist of the GPLv3 is that you're free to sell/modify/redistribute the software as long as your customers have the same freedoms and you need to provide source code for any modified versions you distribute.
Also the freedom must be reality and not theoretical. For example, you can't make it so users can't install modified versions nor may anything you use be a "technical protection measure" for the purposes of the DMCA's anti circumvention clause.