Damn, that's harder to figure out. I'll keep looking and see if I can get hold of a mac to try and work out what is growing on. Until I can, unfortunately the only way to play is with the windows version.
Viewing post in Zen and the Art of Bicycling comments
Sorry it took so long, the log file contains only "Failed to validate Mac AppStore receipt." I googled that and found this unity answers post that says there is a setting to turn off mac appstore validation, sounds like that might be the solution?