[robot]

It is not open source. The source code is open but with an evaluation, i.e. proprietary license:

https://github.com/azure-rtos/threadx/blob/master/LICENSE.tx...

[MarkSweep]

With the odd provision that you can only ship the software on certain devices:

https://github.com/azure-rtos/threadx/blob/master/LICENSED-H...

[lproven]

Article author/submitter here.

This is out of date; the announcement was only days ago, which is why I wrote TFA, and they've not updated the licence files on Github yet.