WAD files like this don't contain any original doom assets and are free to distribute. The files are created by completely independent tools (typically Doom Bu

WAD files like this don't contain any original doom assets and are free to distribute. The files are created by completely independent tools (typically Doom Builder) and only contain binary and text lumps created in whole by the editor. There's no executable code in WAD files that's linked in or becomes a part of the game engine either. You have to have a commercial version of doom 2 to use this level in particular (it cannot run on its own or without the original doom 2 assets). Think of this like a .doc file you're loading in MS Word, but it's new levels for the game. Some total conversions and such could be in a legal grey area or bad place if they take the original assets of the game (sprites, sounds, music, etc) and include them in their WAD files to distribute. There are some projects like Freedoom that recreated the entire asset pack of the original doom games so that someone could use it freely if there are legal concerns.