Since I've been interested in preserving, but also redistributing, and allowing modification and operation of OS/8 and other PDP-8 software, I dug into what licenses are out there.
My take on the licensing situation is:
1. Anything published by DECUS, the Digital Equipment Corporation User Society is fair game. They published their stuff with the explicit goal of wide, unrestricted, dissemination.
2. There are software kits published for operation under SIMH that have various restrictions or lack thereof published with them at [http://simh.trailing-edge.com/software.html](http://simh.trailing-edge.com/software.html):
* ESI-X for the PDP-8 (courtesy of the author, David J Waks).
* FOCAL69 for the PDP-8 (courtesy of Digital Equipment Corporation).
* OS/8 for the PDP-8 (under license provided by Digital Equipment Corporation).
* TSS/8 for the PDP-8 (courtesy of Digital Equipment Corporation).
* 4k Disk Monitor System for the PDP-8 (courtesy of Digital Equipment Corporation).
* CAPS-8 cassette operating system for the PDP-8 (courtesy of Digital Equipment Corporation, prepared by David Gesswein).
3. The OS/8 License included in that kit is the one everyone refers to either directly or by link. The relevant bits are:
1 DEFINITION
SOFTWARE TECHNOLOGY shall mean the sources and binaries to the OS/8, an operating system that runs on PDP-8 computers.
DIGITAL'S INTELLECTUAL PROPERTY RIGHTS shall mean DIGITAL's patent, copyright and trade secret rights in its SOFTWARE TECHNOLOGY.
2 LICENSE GRANT
Digital grants to Customer a worldwide, non-exclusive, royalty-free license under DIGITAL's INTELLECTUAL PROPERTY RIGHTS to reproduce, modify, use and distribute the SOFTWARE TECHNOLOGY solely for non-commercial uses.
So any OS/8 software is fair game.
4. Bob Armstrong pointed out that OS/278 was given in source and binary form to DECUS. It's a work derived from the patent, copyright, and trade secret roots in OS/8.
5. The OS/78 sources are a grey area. They're code lines based on OS/8 that led to OS/278, but not specifically marked "OS/8". The question a lawyer would have to answer is, "What patent, copyright and trade secret rights remain with the stuff that's not already accounted for in OS/8 and OS/278?"
**Probably Irrelevant Point**
Bob Supnik, shared an opinion that PDP-8 and PDP-15 software was marked all freeware by DEC at one point in a discussion thread at: [http://mailman.trailing-edge.com/pipermail/simh/2017-January/016163.html](http://mailman.trailing-edge.com/pipermail/simh/2017-January/016163.html)
He was the one who published the original SIMH kits, negotiated the 36-bit license for the DEC TOPS-10/TOPS-20 software, and I think had a hand in the OPEN VMS Hobbyist License. The OPEN VMS Hobbyist License is actively available from HP at: [https://www.hpe.com/h41268/live/index_e.aspx?qid=24548](https://www.hpe.com/h41268/live/index_e.aspx?qid=24548)
This point is probably irrelevant because he also opined that the documentation of same probably cannot be found.
**BOTTOM LINE**
I think we are 100% in the clear if we include the OS/8 license to redistribute the OS/8 and OS/278 code lines. I'd like to publish the OS/78 code lines, but perhaps we should do so saying they are not explicitly granted permission to be run, that we'll stop redistributing them if asked, but that they're substantially the same intellectual property as what is already available unrestricted in OS/278 from DECUS and OS/8 under the hobbyist license. This is the wheeze that Dave Gesswein uses, for example at: [PDP-8 Disk/Tape Image Information](https://www.pdp8.net/images.shtml)