I took the following from the Overdrive website and I have underlined "at the end of the loan period, titles automatically expire".
Relevant For Today's Learner
School Download Library provides the books students need in the digital formats they want. Media can be enjoyed on laptops, PCs, Pocket PCs, PDAs, Smartphones, and CD or MP3 players, depending
on digital format and use permissions. At the end of the loan period, titles automatically expire. With titles for grade levels K-12, OverDrive School Download Library is designed for anytime access from home.
Additionally, you began your thread with the following:
...CD audio copies of books I've collected that I'd like to put on to DVD's.
This indicates they are yours.
Prof. Honeydew states the following with my emphasis being "kind of indicates"
"The Rules" relate to copyright issues - your post kind of indicates that you may be borrowing audio books from a public library and then making copies of them, which wouldn't be allowed under the CDF rules, as you don't own the original copy.
This post reminds me of Dead Skunk by Loudon Wainwright III.