For whatever's worth, the SGI Free License B 2.0 is now GPL-compatible, being essentially identical to the X11 license, according to the GNU project:
http://www.gnu.org/licenses/license-list.html#SGIFreeB
http://www.gnu.org/licenses/license-list.html#X11License
The SGI Free License B 2.0 is the license under which the GLU tessellator in GLU 9.0.0 has been released:
ftp://ftp.freedesktop.org/pub/mesa/glu/
So go ahead and use the GLU tessellator in your GPL project!