Hello David,
The differences between MQXv5 and MQX 4.2 are best summarized on this page www.nxp.com/mqxv5. Also, just recently launched is the MQX App Builder which is outlined on this page www.nxp.com/mqxappbuilder. To summarize though, moving to MQXv5 you get access to additional protocols such as IoT protocols (MQTT and RESTful API), IPv6 in the TCP/IP Stack (RTCS), Lua scripting language, RPmessage for inter-core communication, and overall cleanup and updating. MQXv5 was based on MQX 4.2 so migrating an application from 4.2 to 5.x is very easy.
With MQXv5 the business model was changed, so yes, there is a license fee involved as outlined on the MQXv5 page I referenced above. The MQX App Builder is included in the license fee for MQXv5. Please send an email to mqxsales@nxp.com if you wish to discuss this further.
Regards,
Doug Bruce
