seL4 was released as open-source in 2014. I know of the helicopter drone; have any other projects made use of seL4? If not, why not? My naive guess is that it's

seL4 was released as open-source in 2014. I know of the helicopter drone; have any other projects made use of seL4? If not, why not? My naive guess is that it's too hard to build on the project without introducing vulnerabilities and therefore negating the benefits of the kernel, but I'd love to be shown otherwise.