Re: License issue with SRFI 5

[Philip McGrath <philip@philipmcgrath.com>]

Hi,

On 10/29/21 10:44, Ludovic Courtès wrote:
> Hi,

This reply has taken a while because I did as you suggested and wrote 
some free replacement documentation (which involved paging back in some 
confusing details[1] and shaving several yaks), so now we have something 
concrete to talk about.

To start with that, my proposed approach, which I hope satisfies the 
FSDG, is here: https://github.com/racket/srfi/pull/15

There are some loose ends to tie up (e.g. I have 48 pull requests open 
making tedious changes to the HTML markup of SRFI specification 
documents to bring Racket's version into alignment with upstream, which 
the current SRFI editor, Arthur Gleckler, is stalwartly reviewing), but 
Guix can cherry-pick it on top of Racket 8.4 (which may be released as 
soon as this week).

The question is, do these changes resolve the situation for Guix (as I 
hope they do for Debian and Fedora, too), or is there anything 
more/different that needs to be done?

> 
> Philip McGrath <philip@philipmcgrath.com> skribis:
> 
>> Since 2005, SRFIs have used the MIT/Expat license, and all but two
>> older SRFIs were relicensed: however, the SRFI editors were not able
>> to contact the author of SRFI 5, Andy Gaynor, so it remains under the
>> original SRFI license.[1] That license, modeled on that of IETF RFCs,
>> was intended to be quite permissive while also trying to ensure
>> derivative works would not be confused with the final, official SRFI
>> itself. (The many versions of some SRFIs that nonetheless have come up
>> while hunting down related issues has given me some sympathy for that
>> goal.) Unfortunately, the restrictions on modifications went to far,
>> at least in the judgement of Debian and Fedora.
>>
>> Here is the license text, as it appears at
>> <https://srfi.schemers.org/srfi-5/srfi-5.html> and
>> <https://docs.racket-lang.org/srfi-nf/srfi-std/srfi-5.html>:
> 
> Oh.
> 
> Do people actually use SRFI-5? (Honest question, I didn’t know about it
> and don’t feel much appeal.)
> 
> Is there code inside Racket that uses it?

In short, no.

When the Debian package maintainer first discovered the problem in late 
2017 [2], the conclusion was that SRFI 5 wasn't used by any other part 
of Racket. The workaround [3] contributed by the Fedora package 
maintainer in early 2018 was to move the offending files into new 
"srfi-lib-nonfree" and "srfi-doc-nonfree" packages and for distribution 
maintainers to patch out the dependencies on them from the "srfi" 
package. This was all to accommodate Racket's exceptionally strong 
commitment to backwards compatibility, because it's a breaking change 
for a Racket package to stop providing a particular module (or 
documentation for a module) without adding an `implies` dependency on 
the new package it has moved to, and Racket packages are never supposed 
to make breaking changes. (The idea is you should make a new package 
under a different name, analogous to how a Debian system could have both 
the "guile-2.2" and the "guile-3.0" packages installed.)

(At the time there were also issues with SRFIs 32 and 29 at the time, 
but those had actually been relicensed to MIT/Expat; it was just a 
matter of resolving lots of confusing different versions of things.)

I then noticed "srfi-lib-nonfree" fly across my terminal, learned of the 
whole mess, and contributed a free reimplementation of SRFI 5 in 2019 
[4], using `syntax-parse` to give vastly better error reporting. At that 
point "srfi-lib-nonfree" became an empty, free package that exists only 
to provide an `implies` dependency on "srfi-lib".

According to [5], though, SRFI 5 is also implemented for Chez, Gauche, 
Larceny, STklos, and Scsh: I'm in the process of adapting my free 
implementation and compatibility test suite, which covers various 
ambiguities and errata [1], to R6RS to send upstream, so hopefully no 
one has to deal with this headache again.

> 
>> Racketeers have high expectations of their documentation, like being
>> able to right-click on an identifier in DrRacket (or the equivalent in
>> Emacs with racket-mode) and jump to the locally-installed
>> documentation for the relevant binding according to lexical scope and
>> the module system---even for a binding like `let`, which is defined by
>> 27 different Racket modules, including `srfi/5`.

[...]

>>
>> This all raises a few questions about Guix policy:
>>
>>   1. Can Guix distribute the official SRFI 5 standard document under
>>      the license listed above?
> 
> I don’t think so; it looks like a non-free software license to me.
> 
>>   2. If not, can Guix distribute free documentation that links
>>      to an online copy of the official SRFI 5 standard document?
> 
> I think it would be easy to do a “clean room” section documenting SRFI-5
> no?  I mean, once you know the spec, documenting it is trivial, to the
> point that it’s even hardly copyrightable (there’s little invention).
> 

This is what I've done.

With these changes, documentation for the `srfi/5` module points to the 
new, free Scribble documentation I've written. That let me remove the 
dependency from "srfi" on "srfi-doc-nonfree", which in turn means that 
"srfi-doc-nonfree" will no longer be a transitive dependency of 
"main-distribution".

>>   3. Would it be permissible for the free documentation to
>>      include instructions for installing the official SRFI 5 standard
>>      document locally, e.g. `raco pkg install srfi-doc-nonfree`?
>>      (Or perhaps `raco pkg install srfi-5-std-doc`, to avoid the
>>      implication of arbitrary non-free materials?)
> 
> Per the FSDG, no.
> 
> [...]
> 
>> However, there are a few less-than-fully-developed sentences in the
>> FSDG that cast some doubt, e.g., "Programs in the system should not
>> suggest installing nonfree plugins, documentation, and so on."[8] I do
>> not think this should be read to prohibit free documentation for free
>> software for referring to restrictively licensed standards implemented
> 
> [...]
> 
> You’re right that the FSDG can be interpreted in different ways.
> Hopefully its spirit is clearer than its wording.
> 
> For this case, I’d take the pragmatic approach (if Debian and Fedora
> haven’t done it way) to either remove SRFI-5 from Racket if it’s
> possible, or to do, like you suggest, a clean-room implementation of the
> code and spec.  Rewriting is likely going to take less time and be more
> fun than trying to disentangle all the issues you mention.
> 

I hope the way I've handled this can satisfy even a much more stringent 
interpretation of the FSDG than the reading I proposed in my last email.

Before I give my opinion, though, let me point to the Scribble code in 
question, from 
<https://github.com/racket/srfi/blob/db6434cd6d2255f223aec3798b45fec368d72131/srfi-doc/srfi/scribblings/srfi-5-doc-free.scrbl#L27-L43>:

--8<---------------cut here---------------start------------->8---
  (define srfi-nf-doc
    '(lib "srfi/scribblings/srfi-nf.scrbl"))
  ]

Original specification:
@seclink[#:indirect? #t #:doc srfi-nf-doc srfi-5-std-taglet]{SRFI 5}

For @hyperlink[srfi-license-history-url]{historical
  reasons}, the SRFI 5 specification document has a
@seclink[#:indirect? #t #:doc srfi-nf-doc srfi-5-license-taglet]{
  restrictive license} and is not included in the main Racket distribution.

The implementation in @racketmodname[srfi/5] and this
documentation are distributed under the same
@seclink["top" #:doc '(lib "scribblings/main/license.scrbl")]{license}
as Racket: only the original specification document is
restrictively licensed.
--8<---------------cut here---------------end--------------->8---

The Scribble sections documenting SRFIs with free specification 
documents begin with "Original specification: SRFI N", where "SRFI N" is 
linked to the installed copy of "srfi-n.html".

In this case, since there will not be a local copy installed, these 
expressions:

--8<---------------cut here---------------start------------->8---
@seclink[#:indirect? #t #:doc srfi-nf-doc srfi-5-std-taglet]{SRFI 5}
@seclink[#:indirect? #t #:doc srfi-nf-doc srfi-5-license-taglet{
  restrictive license}
--8<---------------cut here---------------end--------------->8---

will generate links to 
<https://docs.racket-lang.org/srfi-nf/srfi-std/srfi-5.html> and 
<https://docs.racket-lang.org/srfi-nf/srfi-std/srfi-5.html#copyright>. 
By using those esoteric Scribble incantations, though, the target of the 
link is not resolved until the very last minute, and, if it turns out 
the user has already installed the specification locally, the link will 
point to the local copy.

In FSDG terms, neither the free Scribble documentation nor the docs that 
will be on the Racket website "suggest installing nonfree ... 
documentation". On the contrary, in all three places that so much as 
mention the existence of the original specification document---the one 
quoted above, an almost-empty Scribble file that needs to exist to put 
the document in place on docs.racket-lang.org, and a sort of banner at 
the top of the Racket's copy of the "srfi-5.html" document itself---I've 
given "a clear and serious exhortation" along the lines of the above 
warning that the SRFI 5 specification is restrictively licensed (which 
<https://srfi.schemers.org/srfi-5/srfi-5.html> copy does not explicitly 
point out) and linking readers to the free documentation, instead. Since 
this exceeds the example set by `info "(gcc)Standards"`, I hope it fully 
satisfies the FSDG.

Indeed, if someone does want to use SRFI 5, I hope the new free 
documentation I've written will be more useful than the original 
specification document, since the new documentation addresses the 
confusion and ambiguity [1] I've found in the standard over the last … 
um, over three years, somehow.

> 
> Thanks for raising this issue; HTH!
> 
> Ludo’.

I do think there are some interesting things to think about from a 
philosophical/political perspective. Mostly I find the whole license 
situation quite sad. I think the Scheme community intended to create a 
free license for SRFIs, as evidenced particularly by the fact that, when 
concerns were raised, the editors managed to track down all but two of 
the authors of the c. 77 SRFIs finalized up to that point and 
successfully obtained permission to relicense. I think a sufficiently 
creative lawyer---but I am not any kind of lawyer---could argue that the 
restrictive language should be interpreted as a less well worded attempt 
to state the same substantive requirement as the Haskell Language Report 
License [7] saying, "Modified versions of this Report may also be copied 
and distributed for any purpose, provided that the modified version is 
clearly presented as such, and that it does not claim to be a definition 
of the Haskell 2010 Language." But I'm also glad Guix aims for a higher 
standard than "maybe arguably free"!

Anyway, I hope these changes will finally resolve this issue for Racket, 
but, if anyone thinks something more or different ought to be done, 
please do let me know.

-Philip

[1]: https://srfi-email.schemers.org/srfi-discuss/msg/18709900/
[2]: https://github.com/racket/srfi/issues/4
[3]: https://github.com/racket/srfi/pull/5
[4]: https://github.com/racket/srfi/pull/7
[5]: https://practical-scheme.net/wiliki/schemexref.cgi?SRFI-5
[6]: https://srfi-email.schemers.org/srfi-announce/msg/2652023/
[7]: https://spdx.org/licenses/HaskellReport.html