This is mainly a bug fix release, the release notes are here:
https://issues.jboss.org/secure/ReleaseNote.jspa?projectId=12310200&version=12318669
You can download the source code for this release from:
https://svn.jboss.org/repos/labs/labs/jbosstm/tags/JBOSSTS_4_16_1_Final/
The binary artifacts are available in the JBoss Nexus repository:
https://repository.jboss.org/nexus/content/groups/public/
Enjoy!
The Transactions Team