By the way, all this talk is about the Quake engine and the Quake shareware episode. Just in case that wasn't clear (sorry :)
From the SLICENSE.TXT file:
6. Permitted Distribution. So long as this Agreement accompanies the Software at all times, ID grants to Providers the limited right to distribute, free of charge, except normal access fees, and by electronic means only, the Software; provided, however, the Software must be so electronically distributed only in a compressed format. The term "Providers," as used in the foregoing sentence, shall mean persons whose business it is to provide services on the Internet, on commercial online networks, or on the BBS. Anyone who receives the Software from a Provider shall be limited to all the terms and conditions of this Agreement. Further, ID grants to you, the end-user, the limited right to distribute, free of charge only, the Software as a whole.
Pretty sure you can't include the shareware.
It also specifially states you're not allowed to run custom content with it. And that's beside the fact that including user levels is kind of debatable to begin with.