WinMBF is a source port project by Team Eternity. It is a direct port of the MBF port by Lee Killough to operating systems that support the SDL library. It removes the original low-level system code and replaces it with a modification of the code used by the Eternity Engine. Unlike MBF, WinMBF is available only under the terms of the GPL, since it was based on the GPL-patched MBF source and additionally contains code from Eternity, SMMU, PrBoom, and Chocolate Doom.