Unfortunately, I do not think that you may legally share the works. Their terms of service currently say:

1.2 You may solely for private, educational, personal, scientific, or research purposes access, browse, view, display, search, download and print the Content.

1.3 You may not: [...] re-distribute, reproduce, or transmit the Content by any means including electronic (e. g., via e-mail) nor post it on their personal or public websites or on public networks...

So while you may have the copy of the book legally, it seems unlikely that you can give it to your students. There's always a chance that what they're saying isn't legally enforceable (see non compete agreements), but I don't think that's the case here. I'm not a lawyer, so I can't say for sure.