This is a warning to Oblivion modders and more than likely other games from Bethesda and other developers. There's a site called gmod.com using suspect and underhanded methods to mine content from the major and other mod sites for use on their site. It's also possible that they expect to make money from these files which is strictly against the EULA.
For further information see this thread at Tesnexus and modders should check if their work and personal information has made it to gmod.com and have it removed.
The site also suspiciously wants to install software on your computer which is something browsers should be careful of.
Here are the other topics I couldn't find before and one from the Torchlight modding community.