To some point I have to agree with Halmex, but I wouldn't use the word stupid. Many games are being modded, and in most cases the developers supports that because it usually makes games even better. I don't see any need to close this thread, you should allow it being discussed here even if you don't want to offer any support.
But let's make one thing clear. When you purchase a copy of this software it's your property, as long as you keep it on your own computer you can do with it whatever you like. But in this case, if you modify the files you can not expect any support from the developers. I hope they will change this view.
Btw, I find it kind of strange if Vstep would end up in conflicts with their customers. Maybe Vstep should think twice if they plan new versions and addons in the future..