My objective is to create an online learning website where in, I will be uploading classroom lecture videos. User will login based on credentials but at the
same time I want to restrict the user from downloading the currently playing video or any other video from my website. This means that the video should be
buffered in chunks at the client site, and previously used chunks should be deleted after use, so that complete video never resides on the client machine.

I need some help to understand the underlying technology behind websites such as GMATPill and eGMAT. My specific questions are,

1. Any specific tool that needs to be purchased? How can I create such websites if I want one for myself?

2. If you right click on the video, it seems to be adobe video. But then at times it also allows user interaction, such as clicking on a button on the video to move forward. Also, there is a navigational tree on the left hand side for navigation purpose. Again, if you right click there, it shows it as an video but how does it allow user interaction?

3. Any better way of doing that? Any suggestions? On how can I create a better website than these ones?

4. How to implement DRM if I need to? Costing? Better choice among alternatives?

5. Any other suggestions for online videos that I should keep in mind while developing?

I know about Adobe Flex, but I am open to other alternatives as well.

Please suggest.