There are people on this planet that can easily get rid of the lock. It's Unreal. It shouldn't be that difficult to unlock. People were able to mod skins in AvP 2010 and that uses a completely different engine(I think)
... Like I said. They actively shut down attempts by people in the Duke4 community, which is a very small tightly knit group of people with a number of coders. They were not able to do anything beyond a few texture mods, and that requires using the unpatched version of the game, and some legally shady modifications. It's not easy, and it's not something which can be done wide spread either. There won't be any AXP REALISM mods for Colonial Marines. No modding functionality of any meaningful nature.
Especially if Gearbox makes it a habit of patching the game to lock out changes modders make. There were a couple of people who were making headway with getting a duct-taped version of Unreal ED to work with DNF, along with some other modifcations. Gearbox came in, and made it so that if certain things were set, the game would crash. Literally. They purposely sabotaged efforts.