AAC (ISO/IEC 13818-7:2003)
The AAC audio format patents are licensed via Via Licensing.
The 2004 version of the specification is available from http://jongyeob.com/moniwiki/pds/upload/13818-7.pdf . The document state these terms of use
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from either ISO at the address below or ISO's member body in the country of the requester.