Leading in-memory database vendor Redis is switching to a dual-license approach, imposing far more restrictive terms.
The official announcement of the change gets right to the point:
Starting with Redis 7.4, Redis will be dual-licensed under the Redis Source Available License (RSALv2) and Server Side Public License (SSPLv1).
It is not the first time Redis has changed its terms. Back in 2018 it changed the license on some of its modules in ways which upset a quite a few open source luminaries.
The Reg has previously described Redis as “the most popular database in the world – if, that is, your world is solely within AWS”. Formerly, Redis’s source code was available under the BSD 3-clause license – a permissive one which allows developers to make commercial use of the code without paying.
Soon after that change, one of the other big NoSQL database vendors, MongoDB, also changed its license in an effort to reduce commercial exploitation of its code. It created a new license called the Server Side Public License – which is not liked by some open source folks. Even so, a few years later, Elasticsearch also adopted the SSPL – again to the dismay of some purists.
This controversial SSPL licence is one of the two that Redis is adopting under a dual-license approach, along with the same RSAV that it’s been using since 2018 for some of its modules.
The change will take effect from Redis version 7.4, and we expect that multiple Linux distributors will drop Redis from their codebases. Discussions are already taking place on the openSUSE and Fedora mailing lists.
However, the disruption will probably be modest and temporary, as alternatives are already available – such as the still BSD-licensed fork KeyDB. There’s also Microsoft’s Garnet, although that has the drawback of being writting in C#. Another Redis alternative, Dragonfly, is less likely as it’s covered by the BSL, as recently adopted by HashiCorp.
A predictable response to Redis’s decision is what happened to HashiCorp’s Terraform: the code was forked to become OpenTF, which was later renamed OpenTofu.
These changes reflect the FOSS community’s growing desperation at trying to make open source pay, which has even led to developers sabotaging their own code. Others stop offering free community support, while some are attempting sponsorship approaches.
The SSPL is quite close to the GNU Affero General Public License, or AGPL, and includes most of the text from it – as you can see from this comparison [PDF]. The important difference in the SSPL is its clause 13, which begins:
If you make the functionality of the Program or a modified version available to third parties as a service, you must make the Service Source Code available via network download to everyone at no charge, under the terms of this License.
The traditional GPL requires, among other things, that if you provide your users with executable binary code, you must also provide them with the source code. Back in 2007, the AGPL extended this so that if you provide your users with that code’s function over a network, you must also provide them with the source code, as tl;drLegal explains.
The AGPL is the GPL for SaaS apps: it closes the loophole in the GPL that a SaaS vendor isn’t distributing their code. When the AGPL was still quite new, this was sometimes controversial – and sometimes it still is.
The SSPL extends the AGPL, such that not only must you provide the source code of the app itself but the entire service built around it:
“Service Source Code” means the Corresponding Source for the Program or the modified version, and the Corresponding Source for all programs that you use to make the Program or modified version available as a service.
That’s the part that the open source folks are upset about. According to industry guardian the Open Source Initiative, the SSPL is not an open source license. It reminds us of how terrified big vendors were of the “viral” GPL.
It also puts us in mind of the more recent events around Red Hat’s changes to the ways in which it makes its source code available. This vulture was startled to be invited on stage last month at the FOSDEM conference in Brussels – mostly because he felt compelled to defend Red Hat against accusations of “open washing.”
Arguments like this on Stack Exchange about the important differences between the AGPL and the SSPL will continue. Software is only open source if the OSI says it is, but we feel it’s important to bear in mind that open source is not the same as free software.
There is nothing wrong with making money from free software. Even Richard Stallman says so.
If such licenses help software vendors to make money from their efforts, that is a good thing. If they can do that and also prevent vast billion-dollar businesses from exploiting those product and those companies then, for this writer, that’s better still. ®
