It's a jailbreak app, and so would only be available in the Cydia app store. Check out the Hacker thread and read the sticky posts (at the top of the thread list) for more information. If you are using the forum's app, there is a tab for stickies at the top of the thread list, after you select the proper forum.
Unfortunately, no, there is no App Store equivalent to AppLocker. All you can do is go to Settings and set up some restrictions (so you can turn off buying apps, deleting them, etc.). AFAIK, nothing from Apple will allow you to lock an actual app. Sorry. Marilyn
