There were some minor issues addressed in the last release of
JobRoller v1.6.5, with no major issues reported since that release.
The demo site is fully functional, however data cannot be saved to it which is why you cannot post new listings. There should have been a message pop up prior to the demo site being accessed which confirmed this. Thanks.
(Just to note, I edited the post to update the theme you are inquiring about as it is related to JobRoller not Quality Control)