Hi Marcus,
KSDK 1.3 would be an option for you. However, if you are interested in MQX version 5 (which is an extension of MQX Classic version 4.2), a port to the K81 could be done for you. It is subject to the license fees outlined on this page (www.nxp.com/mqxv5 ) but it has many additional components and updates that might be of interest to you. MQXv5 will continue to be maintained and the license fee includes the first year of maintenance updates.
Regards,
Doug Bruce
