Don't waste your time or money on this software. It used to work ok a few years ago. It no longer functions correctly. It won't snipe on an auction. The developer does NOT provide adequate support. Nor does he deal with issues in a timely manner. You'll end up wasting time reloading and trying to snipe auctions.
If you really need to snipe auctions on a Mac, use something else. Try JBidWatcher. (good) Or AuctionHunter. (very good) At least they will bid, so you actually stand a chance of winning the auction with your snipe.
Please, avoid MaxiBidder. Or at least do your homework first, read thru the support forums at ColourfullCreations. There you'll see how those who have wasted their money are now wasting their time trying to get MaxiBidder to snipe.
Save yourself the headache and heartache, don't lose that auction on eBay because you tried to use MaxiBidder.