IF it is just walkmeshes and such, ok then. But if you need to download the mod, here is what can happen:
1. Players can load it up in the toolset, and find all the secret areas, and goodies.
2. Somehow cheat (I know EFU players wouldn't do this though)
3. re-release it as their own with some changes..
I dunno, just so much BS and last minute bombs dropped. These are major warning signs.