Installation is supereasy. In a standard box with SDL, that would only mean typical extract, configure, make and make install steps. Few minutes are all that you need. Mac OS X and Windows packages are also available.
OpenMortal is practically meant to be a parody, but nevertheless it is a good one and quite joyful to play. Don't expect the same touches and completeness as the original Mortal Kombat. Looking at what has been achieved so far, then it's simply amazing! The characters are for real, at least real persons whose movements are digitized and imported to the game. If you are willing to undertake the tedious steps, the you can also become a character. However, it's safe to say we would not see someone like Goro in the near future :-P
Network play is supported, but no AI means you can not play against the computer. Since that old Mortal Kombat could have such a simple (and dumb) AI in a ridiculously prehistoric machine by today's standard, I bet it's only a question of lack of contribution rather that difficulties. If you're a programmer looking for something for fun, this could be a nice holiday project indeed.
Oh, how I miss Fatality...