Oh, damn, only just checked this page. Apologies! We'll look into it quickly
UPDATE: This seems to be bug in Unity / Apple's code-signing, so we're pulling the Mac build for now. If you've bought a broken copy, please let us know (info@inklestudios.com) with some proof of purchase and we'll supply a Steam key (the Mac version on Steam is fine, for some magical reason). Apologies again.