Hmmm... Now this is a fine line to walk. Assuming that the content was 'all original' and yet the license on the modeller was a closed one as stated, you could be faced with a potential suit even after your work was complete. However, since the material was indeed your artwork I believe the case would come down to s plit decision, in that you may be able to keep the images yet would be forced to purchase an agreed-to license from the GMax creators.
Overall, if it were me, I'd look into this very close before deciding to perform any serious work with the modeller, or simply use another program to avoid the hassles.
S.
Any truly great code should be indisguishable from magic.