To make a statement, there is no download for OFF. Just copy the code below, paste it into a texteditor and save as "index.php"! :) Eventually I'll probably make a downloadable demosite.
Do what you want. You may modify the code, steal the code, copy the code, use the code, anything you want. I want nothing in return. I won't give you any rights or guarantees either. Use at own risk. Code provided as-is. You get the picture? ;) I don't even require the "Powered by OneFileFramework" bit in the footer, but I'd appreciate it if you DID link back to this page. It's completely optional, though.
PHP 4.0 or higher should be sufficient (not thoroughly tested though, let me know if you have any problems). Short open tag is used in the demo wireframes, but is not required. I write code for magic quotes DISABLED, but in theory it should work either way. Register_globals should definitely be off! This has nothing to do with OFF as such, but is a dangerous setting which I haven't bothered to secure the code against since I would never touch a server with this enabled, and neither should you.