We have chosen to not provide this option for now. There are several reasons for this decision:

1. Download costs to us would increase dramatically if people downloaded whole classes at once.
2. We are only able to keep track of which lectures are used by people when they are downloaded from our website or through an embedded link.
3. People are often searching for information about a certain subject and will download specific lectures.
4. Many computer systems crash when trying to download more than 100mb.
5. We have specific agreements with the speakers about how their lectures will be distributed.
6. We have had a few instances of copyright infringement during the past couple years and we are trying to limit those.

We have not precluded offering this option in the future for some or all classes, but have decided that we will not do it right now. Thanks for your understanding in this matter.