The issue is with both forge-unity and the full inspector samples, using unity 4.3.1f1, though I just found out that they must be placed in the Assets folder, not a subfolder of it. That fixed the error, I'm just surprised that the location matters. Also, you might want to update your first post in this thread. There are two links to the trial but they seem to be pointing to different versions. By the way, I hope you will also bring Forge to the asset store along with a more detailed guide. I haven't had a chance to experiment with it yet, but it sounds very promising! Thanks for your help.