Inferno was a commercial attempt at competing with Sun's Java. The plan 9 folks had to shift gears so they took Plan 9 and built a smaller portable version of it in about a year. Both the Plan 9 kernel and Inferno kernel share a lot of code and build system so moving code between them is pretty simple.

The real interesting magic behind Plan 9 is 9P and its VFS design so that leaves Inferno with one thing going for it: Dis, its user space VM. However, Dis does not protect memory as it was developed for mmu-less embedded use. It implicitly trusts the programmer not to clobber other programs memory. It is also hopelessly stuck in 32bit land.

These days Inferno is not actively maintained by anyone. There are a few forks in various states and a few attempts to make inferno 64 bit but so far no one has succeeded. You can check: https://github.com/henesy/awesome-inferno

Alef was abandoned because they needed to build a compiler for each arch and they already had a full C compiler suite. So they took the ideas from Alef and made the thread(2) C library. If you're curious about the history of Alef and how it influenced thread(2), Limbo and Go: https://seh.dev/go-legacy/

These days Plan 9 is still alive and well in the form of 9front, an actively developed fork. I know a lot of the devs and some of them daily drive their work via 9front running on actual hardware. I also daily drive 9front via drawterm to a physical CPU sever that also serves DNS and DHCP so my network is managed via ndb. Super simple to setup vs other clunky operating systems.

And lastly, I would like to see a better Inferno but it would be a lot of work. 64 bit support and memory protection would be key along with other languages. It would make a better drawterm and a good platform for web applications.