AMR codecs incorporate several patents, held by Ericsson, Universite de
Sherbrooke (VoiceAge) and Nokia. VoiceAge claims to provide patent portfolio
for AMR codecs. Depending on law in your country, manufacturers and developers
may need to get a license. Because it is a shared library, you may need special
contract for each one application, which links against this library, directly
or indirectly.

Patent portfolio seems to be licensed by Via Licensing.

Depending on law in your country, you may need a license for distribution, any
use, commercial use or even development.
You don't have permission to distribute the source code and attached .doc file.