Bring the aqua user interface to your Linux systems.
The goal of Mac4Lin for Linux is to bring the aqua User Interface to POSIX Operating Systems (GNU/LInux, FreeBSD, openSolaris). The project is built for desktop environments based on GTK.
Doesn't have quite all the changes as one other similar package that's available. Also isn't completely autonomous like the other package is. The other one is called Macbuntu, and it works a lot better, except I don't believe it's compatible with as many systems as this one is.
Summary
There's nothing wrong with it safety wise. If you want to make your Gnome desktop look like Mac OS X this is a good choice, if the Macbuntu won't work with your system.