Default Mugen title screen.
The image is a screenshot whose contents (being generated from files in the data/ directory) "may be freely distributed and/or altered", according to M.U.G.E.N's License Agreement, as found in the game engine's readme.txt. Whether that warrants a "permission" tag or a "public domain" tag, I'm not quite entirely sure.
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M.U.G.E.N (also written as M.U.G.E.N., MUGEN, or just Mugen) is a free (but closed source...