Derp, didnt know that
If he gives credit then its fine
I disagree.
If the authors don't give permission, then no, it is not fine. Furthermore, this kind of experimental modding should not be released. It is okay to do this kind of modding to learn how things work and how to code and whatnot, but the products shouldn't be released unless they are completely unique. Stealing and re-texturing models (not to mention the theft of the scripts, and all the datablock over-writing that you know in this case is going on) is not something you should be encouraging.
Not saying that you are directly encouraging that kind of behavior, and I'm also not condoning the comments along the lines of "this sucks."
But this along with the fact that he actually released these weapons does indeed suck.
