If I'm remembering correctly, the gl2d3d code was originally written for Quake. In one of the earlier TGE versions (1.2 and below, maybe?) I remember it having all of the copyright/license comments left in. Apparently those are gone now for some reason.
It's since been ported (and possibly updated beyond what's included in Torque) by the DooM Legacy team. You can find the GPL version of the code: here.
It's since been ported (and possibly updated beyond what's included in Torque) by the DooM Legacy team. You can find the GPL version of the code: here.