Well, this notice was posted 5 years ago.
Printed material is copyrighted by the author to protect intellectual property. Quoting whole sections of material without first obtaining permission from the author or properly citing the work that is being referenced is infringement of that copyright and is against the law.
In other words, the owners of this site could get into legal trouble if members are allowed to post material here without proper citations--which could threaten the existence of this site.
If you are unhappy about the fact that AAWS has copyrighted its material, then do not hesitate to contact them.