DDO has a Mac client: http://www.ddo.com/en/game/download There are loads of games that run on OSX, have a look at Steam: http://store.steampowered.com/browse/mac/
Nice of them to make an announcement in game and in the forums... I kind of expect something on the website to tell me it's expected downtime rather then somebody telling me they made an announcement on twitter. Really poor show.