I'm pretty sure there isn't. The restriction is more on the book than on the software used to read it.
The publishers expect to get paid for each person who is going to install and read the book.
There have been quite a few queries from librarians who have similar (not identical) issues,
and I haven't seen an answer suggesting any useful alternatives.
You could try asking Adobe directly, but I'm not too hopeful of a good answer for you. Good luck.