Hello,
Thank you very much for your interest in Texas Instruments solutions for Industrial Automation. The EtherCAT slave stack that is included in TMDSICE3359 is from ETG (ETherCAT Technology Group). For Production usage and licence, pl visit http://www.ethercat.org/. You can get membership in this group which is currently free and that gives you access to this stack.
There are also other 3Ps that provide this stack, maintenance and additional services. Some of these can be found from TI design network. For e.g.,PORT Is here.
http://www.ti.com/devnet/docs/catalog/companyfolder.tsp?actionPerformed=companyFolder&companyId=678
Let us know if you've further qs and have a very happy new year!
Thanks,
-Srik Gurrapu