This is the result of super fans teaming up with Capcom. Back at EVO 2012, Capcom's Christian Svensson was shown SFxMM running on a laptop. Now the great masses can get it - free!
"...huge shoutouts to Zong Hui and A_Rival for their tireless work on this project. While it began as a fan effort, it's since blossomed into the real deal," blogged Capcom-Unity.
Check out the official Mega Man group page to download a free copy of Street Fighter X Mega Man.