Sorry, I should have re-read the Debian FSG before posting. Actually I wonder why they made a different definition for free software compared to the Free Software Foundation:
A program is free software if users have all of these freedoms. Thus, you should be free to redistribute copies, either with or without modifications, either gratis or charging a fee for distribution, to anyone anywhere.
Well, maybe some of the reactions you encountered are due to fact that the license contains this certain point Nr. 4.
If would have chosen BDS, GPL or something like that this would not have happend. And maybe you would have gotten more code (but that's just theory).
I wonder why you didn't chose those pre-existing licenses...
You should also consider that a befenit of making your software free software is support that comes in the form of free advertising. People liking your stuff will be spreading the word (me too). A game that benefited a lot from chosing a free software license was for example Nexuiz.
If you don't want that, make your game a freeware game and impose any restrictions you want. Tell your users what they should and shouldn't do.
I (and a few others) won't bother you again in that case 
TeeTow: What do you mean by hypothetical doomsday scenario? The only hypothetical doomsday scenario I can find is point 4 of your license (and that is extremely hypothetical).
Trust me. No one would be able to sell your game even if that clause was removed, because you offer it for free. Nobody would pay something for it. And if someone finds out how to sell your game, just go the same way and make some money off it 