Unfortunately we require Windows, which is usually an extra cost for Mac.
I think you can make it work on a Mac by creating a dual-boot system (where you boot EITHER into Windows or Mac mode) and there is also VM-Ware's Fusion (see http://www.vmware.com/products/fusion/) that lets you run Windows and Mac programs simultaneously WITHOUT rebooting.
Keep in mind we haven't tested either option (no Macs in our office), but our trial version of Logbook will let you see if it works.