To compile ManaPlus on MacOSX you need to install fink and optionally FinkCommander.
fink cannot run if you haven’t installed the developper tools (Xcode) and X11 (which provides a complete X Window System). Both are included in the install DVDs which came with your Mac.
You can eventually get more information on http://developer.apple.com/ and http://www.apple.com/support/
./fink.sh