Hey meccaroon and Melange Co.
We finally spent some time trying to figure out the issue. Apparently Mac doesn't let you execute files if you're not on an admin account.
We uploaded a second version of Virtual Cottage that has the permissions tweaked in the .app file. However this will get you another error, because we aren't certified Apple developers.
But by continouisly holding the ctrl key and clicking open on the apps menu, you can force the app to open. Detailed instuctions can be found in the description at the top of this page. Unfortunately there is no clean workaround for this.
The only other option would be to get the app via steam, since steam takes care of the permissions nonsense.