I'm not sure if you've noticed but we do have Eliezer's large essay "The Simple Truth" available for free so people can try out the service.

There are two different kinds of freedom. People can download "The Simple Truth" from you without paying anything. They however are not free to remix it and create derivative works based on it.

Most of the other blogs we will be partnering with are written by a sole blogger who will want us to use some form of copyright protection.

On your end I don't see a need to license every recording the same way. Specifically it wouldn't cost much to make an experiement. Two channels with similar LessWrong content. At the start ask every author for permission.

One channel gets a closed license the other gets CC-BY-SA. Both get the same price. It would be interesting to know the practical effects. Does the closed license channel sell better? How widely will the CC-BY-SA content get distributed?