If you don't mind this tangent question...
Is there a microkernel API that has more acceptance nowadays? In other words, where should anyone wanting to work on real world / enterprise systems based on microkernel look?
Is there a microkernel API that has more acceptance nowadays? In other words, where should anyone wanting to work on real world / enterprise systems based on microkernel look?
You nailed it: From day 2 or so we imagined to develop Genode as the future common API for the diverse range of microkernels and showcased the approach with all L4 kernels we could get our hands on. The vision is still to provide a replacement for POSIX in the microkernel world ;-)
Regarding POSIX, we don't think that tools and applications developed for this interface do not fit the microkernel world but on the traditional systems level POSIX (and its tools) is not sufficient to make the best of out of the microkernel advantages. For example, we run libcurl, GPG, libarchive, and coreutils in an orchestrated scenario to implement a robust and secure deployment/installation subsystem in the Genode-based Sculpt OS https://genode.org/documentation/articles/sculpt-19-07.
The kernel is even formally verified, and it's very widely deployed.
The Okl4 kernel in iPhones is extremely limited in its functionality, you could probably run that code even without an Os. It could also be argued if in its current form it is really a microkernel. Furthermore, sel4 and okl4 are not the same product.
(nothing bad on sel4, I have used it myself and I personally know the people behind the project. But it's not what you think it is)