There was, at one time, a mailing list discussing an operating system written in Ada. I think that may be what you're referring to. There was a key commenter named Nick in there, though I don't recall if he was the one that drafted Hi_Level_Design or if he was the one that was going to write the compiler AdaOS was supposed to be built on, but then went incommunicado for a while. It seems to me there was a project here on sf called Bachar that may be related, but last I knew it had no files. I don't...
First things first, I want to give credit where credit is due: Special thanks to...