Note the references to NXP in the Nest OpenThread press release:
I've not tried to compile but the source has #if's for __GNUC__ which means gcc which hopefully means the ARM supplied gcc in KDS.
I also spied references to "class", and a few "virtual"s which makes me hope OpenThread would be friendly to C++.
My quick perusal could not identify or locate any hardware/soc specific code so I don't know if the claim of NXP (presumably KW) support was more "could happen" or "works out of the box."
Anyone else know?
The idea of real KW support via KDS rather than IAR has appeal to me. As does avoiding BeeKit and its codegen wizards.