I realise that I'm using the parentheses incorrectly or at least needlessly
according to the specification. I understand that they add no
machine-readable meaning. I believe that I stated as much earlier on this
thread.
My abuse of the parentheses was an attempt to express something that SPDX
cannot yet express. I am quite willing to give up this abuse in favour of a
better alternative.
My understanding is that the Secondary Licensing provision in the EPL-2.0
is not the same as dual licensing using an OR. From our FAQ (which we're
still working on):
The notion of Secondary Licenses is intended to permit combining content
> licensed under the EPL-2.0 with an otherwise incompatible license,
> specifically the GNU General Public License, v2.0 or greater. This means
> that the content that includes a Secondary License clause may be combined
> with content distributed under the terms of that Secondary License, and the
> combined content can be then be collectively distributed under the terms of
> that Secondary License.
Further,
Is EPL-2.0 with the Secondary License clause considered dual licensing?
> It is extremely close to dual licensing. The EPL-2.0 is the only license,
> until such time as it is combined and distributed with a work under the
> Secondary License. After such time, any recipient of the combined work can
> consider the content licensed under the Secondary License. The original
> work remains under the EPL-2.0 and is never really dual-licensed. Once a
> downstream adopter has received the content under the Secondary License,
> they can modify and further distribute it solely under the terms of the
> Secondary License.
Does this help?
I hope to make our FAQ public later today or earlier tomorrow. That may
provide further context.
Wayne
On Thu, Oct 12, 2017 at 2:21 PM, Wheeler, David A <dwhee...@ida.org> wrote:
> Bradley M. Kuhn:
> > Could you explain a bit further why the extra parenthesis grouping is
> > needed when only ORs are involved?
>
> As you guessed, the parentheses are not *needed*. The SPDX spec says that
> parentheses SHOULD be used when there are multiple license identifiers or
> license refs, but this is a SHOULD not a MUST.
>
> The section you want to consult is SPDX specification version 2.1,
> Appendix IV ("SPDX License Expressions"):
> https://spdx.org/spdx-specification-21-web-version#h.jxpfx0ykyb60
>
> Subsection "Composite License Expressions" says:
> "More expressive composite license expressions can be constructed using
> "OR", "AND", and "WITH" operators similar to constructing mathematical
> expressions using arithmetic operators. For the Tag:value format, any
> license expression that consists of more than one license identifier and/or
> LicenseRef, should be encapsulated by parentheses: "( )". This has been
> specified to facilitate expression parsing. Nested parentheses can also be
> used to specify an order of precedence which is discussed in more detail in
> subsection (4)."
>
> So the spec recommends using parentheses when there are multiple license
> identifiers. Again, this is only a SHOULD, not a MUST. I view this as a
> stylistic recommendation.
>
> --- David A. Wheeler
>
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--
Wayne Beaton
Director of Open Source Projects
The Eclipse Foundation
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