This app (available for a fully-functioning 30-day free trial) will play Blu-rays in either windowed or full-screen mode.
We would like to thank Leawo for sponsoring TMO this week. Listeners of recent Mac Geek Gab episodes have heard discussion of all manner of Blu-ray topics, and one frustration is the fact that the Mac won't natively play Blu-ray disks, even if you've got a USB Blu-ray reader.