That's true, but as a microkernel, seL4 has a very limited scope. It's not in the same ballpark as, say, the Linux kernel. It's more like a hypervisor. [0]

From a quick google, seL4 has around 10,000 lines of C code, whereas the Linux kernel has around 30,000,000.

[0] https://sel4.systems/About/seL4-whitepaper.pdf

Kinda. https://news.ycombinator.com/item?id=27232401

I think CSIRO disbanding the team was a huge mistake, but in any case they weren't producing the kind of success metrics that sustained their funding.