Unfortunately this is a problem that plagues every modding community at some point - thievery. If you have 100% unsubstantiated proof that the coding/mod is indeed yours, then the site should remove it and ban the offender.
Alot of peoples hard work gets stolen because 1) it is difficult to prove 100% the actual creator. And 2) people who claim copyrights don't actually own a copyright, which makes point #1 even harder to do. Mods ARE copyrightable, (though you can't make any $ from them short of donantions) but unless you actually paid the $20 filing fee to the Library of Congress (for USA only) and have had it approved by them (which takes like forever) theres nothing you can legally do about it. Even if you do file and the offender is in another country, there is nothing to be done about it unless you have an international copyright which costs more, takes way longer, and usually isn't something worth a mod for a game. There are unspoken rules in every modding communtiy - if you are going to use others creations within your own :1) ask the original authors permission beforehand - 2) give them credit in your read-me file 3) Respect the original authors wishes - period.