Nope, you'll be able to run it: "Finally, it’s important to note that because Gatekeeper uses the File Quarantine system, it only works the very first time you try to launch an app, and even then only when it’s been downloaded from an app on your Mac like a web browser or email program. And once an app has been launched once, it’s beyond the reach of Gatekeeper." (http://www.macworld.com/article/165408/2012/02/mountain_lion...)