Re: FreeBSD Use Case for Short Identifiers

Steve Winslow

Hi Warner,

Thanks for sharing this. It looks like a good, detailed way to document how the SPDX license identifiers will work for FreeBSD. I've seen several projects implement SPDX identifiers without this level of detail, but I understand the desire to do so here and I think this will be helpful to the community.

I took a quick look at the sections relating to SPDX identifiers. I had a couple of clarifications that might be helpful to consider:

* In section 2, there's a link to There's a page on the SPDX website that is dedicated to explaining how SPDX identifiers work, at -- this might be more useful as a direct link.

* In section 2.5, I note that it states that for the GNU family of licenses, the "-only" and "-or-later" IDs are deprecated and e.g. "GPL-2.0" or "GPL-2.0+" should be used instead. This is incorrect -- it's actually the other way around, the plain identifier or "+" is deprecated and "-only" / "-or-later" should typically be used instead.

To be clear, the "GPL-2.0" / "GPL-2.0+" identifiers remain valid and usable. They are listed as "deprecated" in the section at the bottom of, but they are still valid (and I expect will remain valid). Some projects, such as the Linux kernel, have opted to primarily use this form rather than switching to "-only" / "-or-later".

This is only for the GNU family of licenses (GPL, LGPL, AGPL) -- all others continue to use "+" as the primary way to express "or later version".

I hope this is helpful! Best,

On Thu, Apr 1, 2021 at 6:53 PM Warner Losh <imp@...> wrote:

The FreeBSD project is planning on expanding our use of the SPDX-License-Identifier. Currently, all files have the full license text. We have a mix of files with SPDX ID and those without.

What we'd like to do is expand this so we can accept software that only has a copyright notice plus an SPDX-License-Identifier to indicate the license. To that end, we're trying to craft a policy / document that describes how contributors, users and redistributors of the software can know the license for any given file in the tree.

For the files that have only an explicit license text, it's that license.
For files with both, the explicit license text is the license.
For files with only the SPDX-License-Identifier, the license text can be found in our source tree as src/share/license/<SPDX-License-Identifier>.txt with any copyright notices in the file pre-pended.

To accomplish this, I've started to put together an over-arching FreeBSD policy at which (a) needs to be copyedited and (b) likely needs to have sections 3 & 4 before 1 & 2.

I thought I'd run this by people here for review and/or to evaluate it as a FAQ answer :).


Steve Winslow
VP, Compliance and Legal
The Linux Foundation

Join to automatically receive all group messages.