Thai Tran, Product Manager of Youtube writes:
We’re also testing an option that gives video owners the ability to permit downloading of their videos from YouTube. Partners could choose to offer their video downloads for free or for a small fee paid through Google Checkout. Partners can set prices and decide which license they want to attach to the downloaded video files (for more info on the types of licenses, take a look here).
And a small number of YouTube partners, including khanacademy, householdhacker and pogobat are also participating in the paid download feature of Youtube, where the publishers can set a price for their content which the viewers can pay to download it straight to their PC.
How to Purchase a Video from YouTube?
Purchasing a video from YouTube is very simple indeed. When you are watching a video from any of the participating partner’s page, you should see a download/buy link just below the left-hand corner of the video (Check the screen shot above). If you wish to keep keep track of the videos you have previously purchased, you can go to the “My Purchases” tab under “My Videos.”.
If you wish to participate in this testing, you can find out more about the test and enter your information in this form.