MAMP installs a local server environment in a matter of seconds on your Mac OS X computer, be it PowerBook or iMac. Like similar packages from the Windows- and Linux-world, MAMP comes free of charge.
MAMP is installed in the typical Mac fashion: very easily. MAMP will not compromise any existing Apache installation already running with your OS X. You can install Apache, PHP and MySQL without starting a script or having to change any configuration files!
Furthermore, if MAMP is no longer needed, it is sufficient to delete the MAMP folder and everything returns to its original status (i.e. MAMP does not modify any of the "normal" OS X).