He's serious.
Apple seriously hates Java. Don't expect to do much with Java on Apple products. This isn't the only Java game I've ran across that has issues with MacOS. If you don't like rebooting a system to play, booting a second OS with MacOS still running (so you don't have to reboot and manage multiple boot partitions) is possible. Just one of several articles I found: http://osxdaily.com/2012/03/27/install- ... irtualbox/
edit: fixed a couple typos