question about Torque and GNU Software

Hi, we're working on a flight simulator game that is going to be distributed under the GNU license. The software itself is free, but we will charge for the media as dictate the GNU license. We bought the Torque engine to use it in future projects, but we thought to use it to build a frontend (just the frontend) to the flight simulator binary. Does it count as a commercial product bound by the Torque license?

PS: The frontend will be closed-source.