If your Mac Book is an x86 architecture, i.e. one of the newest Mac Books, then you can load a live Linux like Knoppix and use that to complete the challenges. If it is an IBM chipset architecture, then I believe that PuppyLinux and a couple of others will aid you with a Live distribution or dual boot mode. Another thing is, who cares if there doesn't already exist a good hash brute forcing program on Mac, Mac comes with all of the development tools, so why not make your own? This may seem like a wild challenge, but hash brute forcing is a dictionary attack. You just need a dictionary of hashes for different length password, random- (i.e. combinations of letters) and real word-based, and several algorithms especially the most popular ones, like MD4, MD5, and SHA1.