Well the survey would include Contiki if engineers chose to mention it.
This survey indicates that less than 2 percent +/- about 2 percent of engineers are using Contiki.
But as you indicate, engineer usage is not the same as installation base.
OOPS, sorry, I switched colors so your comment is right. I wonder however if those figures (all, no only for uC/OS) refer to effective use or are only "intend to use sometime in the future". I remember a few years ago this issue was raised for this or another similar research.
What are the engineering and design challenges in creating successful IoT devices? These devices are usually small, resource-constrained electronics designed to sense, collect, send, and/or interpret data. Some of the devices need to be smart enough to act upon data in real time, 24/7. Are the design challenges the same as with embedded systems, but with a little developer- and IT-skills added in? What do engineers need to know? Rick Merritt talks with two experts about the tools and best options for designing IoT devices in 2016. Specifically the guests will discuss sensors, security, and lessons from IoT deployments.