I’ll cut to the chase – NO, DO NOT DOWNLOAD this “software”.
MacKeeper is one of those apps that seems to pop up everywhere offering to fix all over your problems and more or less upgrade your life along with it. Do not fall foul of this software, far more people report problems with it than you can shake a stick at. They’re marketing tactics alone should warrant serious concerns a lá Parallels.
There are precious few tools that I’ll recommend for any platform in addition to the tools that arrive natively on these platforms. OSX has some neat built in maintainance tools that you can use, if you leave your Mac on overnight it will probably execute a bit of maintainance for you without any prompting.
Generally I find the tools offered by Piriform to be excellent. Their CCleaner app is available for PC and Mac and I make use of it all my machines Windows and OSX.
If you have been duped into downloading the trial for MacKeeper, get it off your system, NOW and never look back.