As a mapper for the Unreal Tournament Community I know that curtain custom maps, weapons or character mods from other games without written approval from the game maker is illegal especially in Epic Games EULAs and policies. But is this illegal in Volition and Deep Silver's view?
http://www.gta4-mods.com/misc/saints-row-mod-pack-f23707
http://www.gta4-mods.com/misc/saints-row-mod-pack-f23707