The "H" in the title signifies mature themes, which are often integrated into specific finishing moves or character interactions unique to this version of the engine.
You can expand the roster by downloading new character folders and adding their names to the select.def file located in the data folder. Is it Safe and Legal? mugen-h-slime-plus
M.U.G.E.N is . However, since these "Slime Plus" builds are community-made and often include copyrighted characters from various franchises, they exist in a legal "grey area." Always ensure you are downloading from reputable community sites to avoid malware. The "H" in the title signifies mature themes,