This is OSX's gatekeeper going crazy because our codesign included the icns file (which then got compressed and no longer verifies). I'm uploading a new package right now. As a workaround you can go to security in system settings, set it to allow anything to run, open LightTable.app, close it and then re-enable the old gatekeeper setting. LT will open fine thereafter. Or you can just redownload in about 2 minutes.