Omniscient is a super simple Doom IWAD patcher, allowing you to patch/convert between most versions of every major IWAD. It’s written using native Win32, and supports all versions of Windows down to 98!. For non-Windows users, it also works perfectly under Wine.
Omniscient is not open-source at this moment as the repository currently contains over a gigabyte of IWAD files that cannot be freely distributed. In the future I may provide source bundles with pre-generated patches and the IWAD files removed.