differences between zephyr and riot.

riot seems a serious competitor of zephyr.

we should be looked into in more details.

Some first impressions:

- Zephyr is not brand new: based on commit history, it looks like an Intel
/ WindRiver product which has existed for some time, rocket os ?

- Zephyr's choice of license (Apache) is surprising for something under the
Linux Foundation umbrella which champions (L)GPL licences -- for example:
RIOT's license, which is LGPLv2.1.

- Zephyr supports few boards, and does not seem to target smaller hardware
based on 8bit, 16bit, or lower-end 32bit (for instance Cortex M0). On the
contrary, RIOT supports all of these, as well as bigger 32bit hardware
(Cortex M3, M4, x86)

- Zephyr seems to impose a mode of operation with a single thread when
there is not plenty of memory, contrary to RIOT.

- Zephyr seems to be using Contiki's network stack, which in our opinion is
suboptimal.


This week some RIOTers have a booth at Embedded World in Nuremberg, where
Zephyr also has a booth + talk. Maybe we get some more info at this
occasion.

If you (or anyone else) have more infos, impressions or opinions, please
share!