Re: What licenses should be included in /usr/share/common-licenses?

Hi all,

On Tue Apr 28, 2026 at 7:38 PM CEST, Simon McVittie wrote:
> With hindsight, having the + syntax for "or any later version" was 
> perhaps premature optimization - it seems to be only the FSF licenses 
> where this concept is frequently used. Other licenses tend to either 
> hard-code the upgrade mechanism in the license itself (like CC-BY-SA and 
> MPL do), or not have one.

As the semantics of the plus sign are codified in the machine-readable 
d/copyright format, section 7.1 [1]:

> When the license grant permits using the terms of any later version of 
> that license, add a plus sign to the end of the short name

...which aligns with the SPDX semantics [2]:

> An SPDX License List Short Form Identifier with a unary "+" operator 
> suffix to represent the current version of the license or any later 
> version.

...it's currently the only way to express "GPL 3 or later" in 
a d/copyright file with a format that is compatible with both our spec 
and SPDX. I do agree that it's a somewhat easy to mess up, though.

> I think it would make a lot of sense to align with SPDX, even if their 
> names aren't always the names we've historically preferred for each 
> license. Notably, SPDX uses "MIT" for "the" MIT/X11 license, 
> specifically the one that is used by e.g. Expat, which is neither the 
> only license used by MIT nor the only license used in X11 - but I think 
> that ship has sailed and "MIT" is a more-widely-understood name for it 
> than "Expat".

I've been using "MIT" instead of "Expat" for a while in new packages, 
and the former FTP Team has never complained about it (I don't know about the 
DFSG Team's stance on this though). When doing so, I would add a Comment 
field like this:

    License: MIT
     Permission is hereby granted, [...]
    Comment: MIT is used instead of Expat, aligning with SPDX. See 
    <https://lists.debian.org/msgid-search/[email protected]> 
    for reference.

I think there are some packages which don't even add such a comment.

>>We could even adopt the SPDX-License-Identifier: syntax.
>
> I don't think that would be appropriate: SPDX-License-Identifier 
> normally means "the license of the file where this marker appears is the 
> named license", but in d/copyright the meaning we want is "the license of 
> some other file is the named license".

+1. Also, "License" is easier to write.

Bye :)

[1]: https://www.debian.org/doc/packaging-manuals/copyright-format/1.0/#license-short-name
[2]: https://spdx.github.io/spdx-spec/v3.0.1/annexes/spdx-license-expressions/#simple-license-expressions