Add AGPL recommendations (#151)

Signed-off-by: Steve Winslow <[email protected]>

Author: swinslow

agpl-recommendations.md

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+# Third Party Dependencies that have been Relicensed to AGPL
+
+## Background
+
+CNCF's IP policy is set forth in the [CNCF charter], section 11.
+
+Under the IP policy, CNCF projects use Apache-2.0 for their code. The CNCF
+Governing Board reviews and approves other non-Apache-2.0 licenses, for
+code in the repos or dependencies of CNCF projects, on an exception basis.
+
+The CNCF Governing Board has previously adopted an [Allowlist License Policy]
+that permits most permissively-licensed components to be automatically
+approved as exceptions, when used in an unmodified manner.
+
+However, components under other licenses -- particularly under copyleft-style
+licenses -- remain subject to approval by the CNCF Governing Board. This is
+not because such licenses are inherently problematic, but rather because
+they may add obligations that would not be expected by, or acceptable to,
+users of CNCF's projects under Apache-2.0.
+
+## Recent changes to dependencies' licenses
+
+Recently (in early 2021), CNCF projects have discovered that some existing
+dependencies they use have been relicensed by their licensors from
+Apache-2.0 to the GNU Affero General Public License v3.0, [AGPL-3.0].
+
+The AGPL-3.0 license is a free and open source software license. However,
+it is a strong copyleft license, which means that when used or distributed
+in certain ways, it imposes copyleft obligations that go beyond the more
+permissive requirements of Apache-2.0.
+
+In addition, portions of AGPL-3.0's copyleft obligations apply to contexts
+where the AGPL-3.0 software is interacted with through a computer network.
+In the context of cloud-native software, this means that copyleft
+obligations may come into play under AGPL-3.0 where they would not for
+other GPL licenses, where distribution is the primary relevant trigger.
+
+This can present a problem for CNCF projects, where the license of the
+component they depend on was previously aligned with the CNCF project's
+own license, but is no longer aligned.
+
+## Recommendations
+
+There are a few approaches that CNCF projects should consider taking, for
+dependencies that fall into this category.
+
+### Switch to an alternative component
+
+The project will likely want to evaluate alternative components with
+similar functionality, and switch to one that is Apache-2.0 or that has
+a permissive license under the [Allowlist License Policy].
+
+### Freeze the component at the version prior to the license change
+
+As a short-term solution, the project might consider freezing the version
+of the component so that it is fixed at the last release prior to the
+license change.
+
+This is unlikely to be tenable as a long-term solution, particularly as
+the prior release is presumably unlikely to continue receiving maintenance
+updates, security fixes, etc.
+
+### Seek an exception from the Governing Board
+
+If the project requires the now-AGPL-3.0 component as a mandatory
+dependency, it can request that the Governing Board grant an exception
+to the license policy.
+
+Please be aware that this is **highly** unlikely to be granted, and that
+the Governing Board has (at the time of this writing) not previously
+granted any exceptions for components that are under AGPL-3.0.
+
+If you do seek an exception, you will want to provide information about
+the specific component(s) and how they are being used. In particular,
+provide details about the boundaries and interactions between the project
+code and the third-party component, and whether the component
+is mandatory or optional for use with the project.
+
+The Governing Board may refuse to grant exceptions at its discretion;
+however, some of the considerations that the Governing Board might take
+into account are as follows:
+* if AGPL-3.0 code would be included directly in the source code repo,
+this is extremely unlikely to be approved as an exception.
+* if use of an AGPL-3.0 component is mandatory to use the CNCF project,
+it is highly unlikely to be approved as an exception.
+* if the component is an _optional_ run-time dependency, and is not
+enabled or incorporated by default, it may be more acceptable as an
+exception.
+  * additionally, if the optional AGPL-3.0 component's licensor has made
+  available interface tools (such as client libraries) that are under
+  Apache-2.0 or a similar permissive license, that may also make it more
+  acceptable as an exception.
+
+[CNCF Charter]: https://github.com/cncf/foundation/blob/master/charter.md
+[Allowlist License Policy]: https://github.com/cncf/foundation/blob/master/allowed-third-party-license-policy.md
+[AGPL-3.0]: https://www.gnu.org/licenses/agpl-3.0.en.html