My current pastime has been looking at rxDOS with its quite an odd history. To the best of my knowledge rxDOS was written by Michael Podanoffsky and was included with his book `Dissecting DOS’ in 1994. The version of rxDOS, included with the book, is marked RxDOS Version 6.00. In 1999, the rxDOS source was released under GNU Public License and is marked version RxDOS Version 7.1.5.
I said odd earlier because sometime in 2008 C. Masloch ported the 7.1.5 source from the original MASM source to NASM and released RxDOS 7.20N for developers.
Do not use RxDOS version 7.20N. It tries to re-produce every bug of RxDOS 7.1.5 (as found on the FreeDOS mirrors). It is not usable currently. The release of version 7.20N is only intended for developers.
rxDOS readme
From 2008 through 2018, rxDOS versions 7.21 through 7.25 were released. I am not really sure about the 7.25 version being released, but that is what the source claimed. All the versions from 7.20N through 7.25 are tagged in my Gitlab.
I have not seen any announcements, but it looks like there is some rxDOS work that I found on the pushbx.org/ecm/web/ site. The rxDOS updates are listed here. Also, E. C. Masloch’s Gitgub repo. Another interesting page is 25+ YEARS OF DOS HISTORY that seems its last update was 2006-09-03.
Anyway, my main interest is going through Podanoffsky’s Dissecting DOS to pass some of the winter days until I get bored. The original source uses MASM 5.1 and from a quick check the source compiles with this version. I use either wasm from Jiří Malák’s Open Watcom v2 build or a current version of UASM* which is currently version 2.56 as of October 2022. As a note, the UASM website triggers Norton giving Dangerous Webpage Blocked which in my experience is not correct. Finally, I only have the 2008 and newer sources for reference. I just do not use NASM and really have no plans to learn it.
All the sources I mentioned above are on my Gitlab account and on my home account.
ecm here, the one who once thought her best bet was using RxDOS as a base for lDOS. My v7.24 release was the last proper release, which is visible in the download directory as the last version is RxDOS-7.24.zip: https://pushbx.org/ecm/download/
I did update the version numbers in the sources and docs to v7.25 on 2018-10-08 but this was in preparation for a next release, not the final revision that would be a release: https://hg.pushbx.org/ecm/rxdos-7.2x/rev/40fd993b55e4
The releases all have an entry in https://hg.pushbx.org/ecm/rxdos-7.2x/branches
Nowadays I do contribute to the FreeDOS kernel sometimes. Since 2023 August I have collected some patches to Enhanced DR-DOS, based on the 1997 release of OpenDOS v7.01 and the subsequent work of the DR-DOS/OpenDOS Enhancement Project. Since 2024 April I have also worked on a fork of the MS-DOS v4.00 source release.