This is the full version of OldSkool. Included are the menu enhancements, singleplayer, mutator, HUDs, Unreal I models, team skins for them by Psychic_313, and Real CTF skins. Note that this package is nothing more than a combination of Oldskool Amp'd Lite (which is included in many UT singleplayer mapPack downloads) and the Unreal I models Full packages.
If I use Enforcer in single player and switch off it i can never select it again. How do I fix this?
According to the html file, this is actually the (no UMOD) full 2.39 version from 9/10/2001.
edit: There are multiple files inside, including two .umod's.