PiDP-8/I SoftwarePDP-8 Software Licensing
Not logged in

PDP-8 Software Licensing

(1) By Bill Cattey (poetnerd) on 2019-10-20 03:30:46 [link] [source]

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

    • 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:


    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.


    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.

  1. 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.

  2. 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:

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:

This point is probably irrelevant because he also opined that the documentation of same probably cannot be found.


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

(2) By Bill Cattey (poetnerd) on 2019-10-20 03:40:11 in reply to 1 [link] [source]

I just found this explicit statement from Bob Supnik in alt.sys.pdp8 that also provides the license, and the statement that redistributors of OS/8 should include it.

(3) By Warren Young (tangent) on 2019-10-20 21:32:54 in reply to 2 [source]

We already include a copy of the OS/8 license here and reference it here.

I infer that you're considering checking more DEC and DEC-derived OS sources and resulting binaries into the repo. Unless there's a clear license for it, please don't.

Consider the case of ETOS, which we only have vague a third-hand acceptance for, so I pulled it from this distribution, where it was sitting, passively because it was in Oscar's 2015.12.15 distribution.

There are ways to remove artifacts from the repo after the fact, such as due to copyright violation, but it's better not to check things in before the licensing is clear. I did do this for ETOS, but realize that Fossil shunning is specific to a single repo only; anyone who cloned this repo before I shunned the ETOS artifacts still has those artifacts in their local clone(s). The only way to get rid of it everywhere is to convince everyone who has a clone to:

  1. ...also shun those same artifacts on their clones; or

  2. ...delete their clone(s); and/or


(4) By Bill Cattey (poetnerd) on 2019-10-20 21:43:11 in reply to 3 [link] [source]

I infer that you're considering checking more DEC and DEC-derived OS sources and resulting binaries into the repo. Unless there's a clear license for it, please don't.

Understood. Agreed.

It looks like anything clearly labeled OS/8 is fair game. So the OS/8 Combined Kit stuff I have acquired is fine. It's clearly labeled OS/8, and it clearly aligns with the license. (And it's quite complete!) From that base we can, in fact, create a "Build from source, all of OS/8 v3d including FORTRAN II, FORTRAN IV, BASIC, and MACREL, with the latest patches."

I totally get the ETOS thing.