http://clhs.lisp.se/Front/Help.htm#Legal >Permission to copy, distribute, display, and transmit the Common Lisp HyperSpec is granted provided that copies are not made or distributed or displayed or transmitted for direct commercial advantage, that notice is given that copying, distribution, display, and/or transmission is by permission of LispWorks Ltd., and that any copy made is COMPLETE and UNMODIFIED. IN PARTICULAR, the material that MUST appear in the copy includes:

>...

>Permissions related to performance and to creation of derivative works are expressly NOT granted.

>Permission to make modified copies is expressly NOT granted.

>Permission to add or replace any links or any graphical images to any of these pages is expressly NOT granted.

It's one of the most restrictive licences.