This hack gives developers access to everything XNA restricted before. Obviously this isn't the first hack for the Zune, but it's described as the "first true hack,".

The hackers have released OpenZDK as well; a development environment for Zune software, which can be used to develop about anything that couldn't be done because of the XNA restrictions -- like games, emulators, etc -- it also creates room for possible alternative app stores, like Cydia for jailbreaked iPhones.