While the courses aren't directly accessible without internet, there are some portions you can download
The courses listed as "New" on the course site feature downloadable videos that can be watched offline. You can find that list here: https://courses.dts.edu/collections/new. There are also a number of other courses that have downloadable videos.
If a course's videos are downloadable, you'll see a download option when viewing any section video (in the top right, above the video):
PC / Mac
iOS / Android
However, other course components, such as quizzes and discussion questions, require an internet connection. Recognizing that internet access may only be readily available in some places, we are pursuing additional offline options for accessing course content.