First, the boot disk that is available on bitsavers is one for the Omnibyte OK68K1A board, the (as far as we know) original implementation target for the 68k port of Idris.

The rediscovery of Idris started with a posting on the vcfed forums about a strange Idris-based 68k-based machine that showed up in Mattis Lind’s hands in Sweden.

https://forum.vcfed.org/index.php?threads/pd68-68000-based-vme-system-running-idris.1252893/

Back then, I started to analyze the disk image provided by Mattis and wondered if this was a starting point to recover the (at that time) lost Atari ST port. All that remained of that port on the net was a low-res picture of a Mega ST running X10 on Idris on the Idris Wikipedia entry:

https://en.wikipedia.org/wiki/Idris_%28operating_system%29#/media/File:Atari_Idris_XWindows_1.jpg

The rediscovery of Idris for the ST, then, was a happy coincidence. I started to look for further information about Idris and came across a 1986 Usenet posting by Skip Tavakkolian, whom I knew from his work on Plan 9 (but I wasn’t aware he was involved in the Idris port until then).

https://groups.google.com/g/comp.sys.atari.st/c/QftYKOLSQEg/m/zTPemnfNu4cJ

Luckily, Skip still had a set of Idris floppies and also found and scanned the original documentation. He was so nice to provide all of this, but unfortunately the Idris hard disk driver used an approach to ACSI interrupt handling for which Hatari’s emulation was too fast (details on request, that’s a longer story – and HD emulators such as ASCI2STM currently also do not work on real hardware). Luckily, as you mention, some of the Hatari developers were able to fix the timing problem – this involved a bit more effort than just adding a delay.

I’m in contact with the current copyright holder of Idris. They are very friendly and supportive and have started looking for the source code but I don’t have too much hope, since they were not aware that they own the product (but let’s see what they may still find). The Idris distributions available (there are copies of versions 2 and 3 now) only contain example source code for the assembly startup and device drivers, but it’s possibly to compile these and link a new kernel either on the ST version or using an Idris user space emulator which I’m going to release in the next few days.

I’m going to write an article about the story of the recovery of Idris later this year and just submitted a talk proposal for the next meeting of the German Unix User Group (GUUG) in March.