Could I put my video ripping script behind a locked section of a forum and setup a subscription service for people to use it? The script consists of about 4 folders with various files in each.

If this can be done how would I do it? I dont want to just link to it as other people could pass the linkout to friends etc

You can set up subscriptions on a forum. How will depend on the forum software you're using. I think subscription functionality is built into vBulletin. If not it's a module you add. I would think it's similar with other forum software, though some might require custom programming.

You'll also need some way to collect payment and hook that into the subscription system.

use Vbulletin you can set it up easily on that, it comes with the script. you better hurry though, their doing a price increase on June 2nd..

nice idea too!

You'll also need to set up some basic server side protection to prevent hotlinking to the files. That is, only allow access to the files from special scripts in your website.

In the past when I've had to do this, I've always placed the restricted files outside of the web root and used a dynamic language (PHP, usually) to read the file in, spit out the correct header, and flush the buffer to the browser. That usually works. You can even specify a header type of attachment to force a download. Doing things this way guarantees the greatest possible security.