I didn’t see this particular topic addressed in the specification (although I’m happy to be correcedt if I missed it), so I thought I’d post and see whether there is a solution that’s commonly used, or if there’s room for a new identifier.
Virtually all so-called “permissive” licenses permit the recipient of code to license out under different terms, as long as all the requirements of the in-bound license are met. In almost all of these permissive licenses those requirement boil down to:
- Preserve all existing IP notices (or in some cases, just copyright notices)
- Provide a copy of the license (or something to that effect: retaining “this permission notice” (ICU/Unicode/MIT) or “this list of conditions” (BSD) or providing “a copy of this License” (Apache 2.0))
The rules around element 1 and SPDX are well-described.
With regard to element 2, a fully-compliant but informative notice when there is a change from the in-bound to the out-bound license would look something like this (with the square bracketed part being an example of a way to say this):
SPDX-License-Identifier: MIT
[This file/package/project contains code originally licensed under:]
SPDX-License-Identifier: BSD-2-Clause
The point being to express that the outbound license is MIT, but in order to fully comply with the requirements of BSD-2-Clause, one must retain “ this list of conditions and the following disclaimer” which including a copy of BSD-2-Clause accomplishes. Without the square bracketed statement above, it seems confusing as to what the license is (or whether, for example, the code is dual-licensed MIT AND BSD-2-Clause.
One way to do this I suppose is to use the LicenseComment: field to include this information, but it seems to me that this is enough of a common situation that there ought to be something more specific to address this situation.
Thoughts? Am I missing something?
