XMule
xMule
xMule is a fork of LMule, and was the defacto eMule client for Linux until aMule appeared and challenged that position. However, xMule is still under active development, primarily by HopeSeekr, the person who originally forked lMule.
As of version 1.8.4, the xMule client is banning aMules (all versions) and eMules (version 0.43 and up). This is due to the developers of xMule being of the opinion that those clients are leeches. Please refer to the xMule website for more information on its current progress.
aMule is a fork of xMule, though both projects have moved further and further apart since then. Diplomatic relations between the two projects are sadly in a rather sorry state.
NOTE: aMule is a separate project and is not related to xMule in any way (apart from being originally a fork from it).