This appears to copy the AARM but the bottom of the site claims to be licensing everything under Apache 2.0 and neglects the actual copyrights on the text. They can be seen here:

http://www.ada-auth.org/standards/2xaarm/html/AA-TTL.html

That's not a terribly good idea in general. Interestingly, for the Style Guide they were at least courteous enough to note the original license, but not the AARM.