Redis and Terraform Left Open Source the Same Way. Only One Came Back.
Redis and Terraform both left open source for a more restrictive licence within months of each other, and outside groups copied each one within weeks. Only Redis came back; for Terraform, the copy became the lasting open version.
- Subject
- What leaving open source costs a vendor
- Published
- 19 AUG 2026
- Reading time
- 8 min
- Film
- Watch · 4:04
In short
- What it is
- A third kind of licence sits between open source and proprietary: read and run the code free, but don’t resell it as an online service.
- What happened
- When the makers of Redis and Terraform, two widely used developer tools, tightened their licences, outside companies kept open-source copies going within weeks.
- Before you adopt
- Before you rely on an open-source tool, ask whether others could realistically keep it going if its owner changed the licence tomorrow.
In this post · 5 sections
Any business that builds on open source depends on licences, and where one company owns a tool, it can change that tool’s licence for future versions. The owners of Redis, a database, and Terraform, HashiCorp’s cloud infrastructure tool, did so about seven months apart, moving to licences that aren’t open source. Each time, a neutral foundation and several companies carried on an open copy within weeks. That mattered more than the licence text.
A third category between open and proprietary
Proprietary software gives no source code at all. Open source gives the source under terms that let anyone use, modify and redistribute it, even as a competing product. A permissive licence asks almost nothing in return; a copyleft one asks that anyone who redistributes a changed version shares that version’s source too. Source-available code sits deliberately in between: visible and usually free to run, but blocked from one specific use, almost always a competitor reselling it as a hosted service.
Move a project away from open source, and its users can answer with a fork — a copy of the code that a new, independently run team keeps developing on its own.
What happened to Redis
Redis started under a permissive Berkeley Software Distribution (BSD) licence. In March 2024, Redis switched to a choice of two licences, the Server Side Public License (SSPL) and the Redis Source Available License (RSAL). Both are source-available, not open source. Redis said they were aimed at cloud providers who “commoditize” its work by reselling Redis as a hosted service.
Redis, “Redis Adopts Dual Source-Available Licensing”, March 2024. redis.io
Within days, the Linux Foundation, a non-profit that hosts shared open-source projects, announced Valkey: a fork of the latest BSD-licensed Redis release at the time. AWS, Google Cloud, Oracle, Ericsson and Snap backed it, and a committee of former Redis contributors, not one vendor, runs it.
The Linux Foundation, “Linux Foundation Launches Open Source Valkey Community”, March 2024. linuxfoundation.org
About 13 months later, Redis reversed course. In May 2025, Redis added the GNU Affero General Public License (AGPL) as a third licensing option, alongside its existing SSPL and RSAL choices. The AGPL is a copyleft licence that adds a separate duty: offer the source to anyone who uses a modified version over a network, even when nothing is ever formally distributed. Salvatore Sanfilippo, Redis’s original creator, had rejoined the company in late 2024. Redis’s announcement names his guidance, and that of its technical chief and core developers, behind the move to a licence the Open Source Initiative, the body that approves open-source licences, recognises as open source.
Redis, announcing the return of the AGPL option, May 2025. redis.io/blog/agplv3
What happened to Terraform
HashiCorp’s move came first, about seven months earlier. In August 2023, HashiCorp relicensed Terraform, along with the rest of its product line, from the open-source Mozilla Public License (MPL) to the Business Source License — a source-available licence that blocks competing commercial products built on the code.
HashiCorp, “HashiCorp adopts Business Source License”, August 2023. hashicorp.com
Within weeks, a coalition of contributors and companies published the OpenTF Manifesto, calling on HashiCorp to reverse course. HashiCorp didn’t, and the fork went ahead anyway.
OpenTofu’s community manifesto, published in response to the relicensing. opentofu.org/manifesto
Renamed OpenTofu and taken in by the Linux Foundation within weeks, the fork is steered by multiple companies rather than one vendor. The Linux Foundation says the fork had formal pledges of support from “140+ organizations and 600+ individuals”.
The Linux Foundation, announcing OpenTofu, September 2023. linuxfoundation.org
Unlike Redis, HashiCorp never reversed course. HashiCorp itself was bought by IBM in a deal that closed for $6.4 billion in February 2025, and, as of September 2026, Terraform remains under the Business Source License, now as an IBM product.
TechCrunch, on IBM closing the HashiCorp deal, February 2025. techcrunch.com
An open-source licence that also covers hosted services
Both cases turned on what triggers each licence’s obligations. A permissive licence like MIT or the Apache License asks almost nothing: you can ship the code inside a closed product without sharing anything back.
A copyleft licence like the GNU General Public License (GPL) asks more, but only when the code is distributed: modify it and hand out the result, and the recipients are owed the source. Run that same modified code as a hosted service, known as software as a service (SaaS), and nothing is ever distributed, so nothing is owed. That gap is the SaaS loophole, and it let cloud providers build hosted services on open-source databases without being obliged to share their changes.
AGPL closes exactly that gap. Its added clause triggers on network interaction, not distribution: if users interact with a modified version over a network, the operator owes them the complete modified source, whether or not any code ever changed hands. That makes it the natural choice for Redis’s return to open source. It aims at the same target as the Server Side Public License and the Business Source License: a cloud provider running the code as a hosted service without sharing back. Unlike those two, it still counts as open source by the Open Source Initiative’s definition.
For engineersThe exact trigger language, for anyone checking a dependency's licence themselves.
The GPL’s copyleft duty is triggered by “conveying” the software — roughly, handing a copy to someone else. The AGPL adds one clause: interacting with the software “remotely through a computer network” counts too, so a SaaS operator running a modified copy owes users the source even though no copy is ever handed over. The SSPL takes a different route to the same target: instead of extending what counts as distribution, it requires anyone offering the software as a service to release the source of the entire service stack around it, not just the software itself. The Open Source Initiative (OSI) has said the SSPL isn’t open source because it singles out one field of use: offering the software as a service.
Primary texts: the GNU Affero General Public License, section 13; the Server Side Public License, section 13; and the OSI on why the SSPL doesn’t qualify.
The licence didn’t decide this. The fork did.
The choice is whether others could carry on without the vendor
What restrains a vendor’s licensing choice is whether a credible fork is possible: a real contributor base and a neutral foundation willing to host it. Redis and Terraform had both, which is why both were answered within weeks.
Before you build on a critical open-source tool, check its licence, then ask whether others could realistically fork it if the vendor changed that licence tomorrow.
Updated 26 Sep 2026: we corrected how quickly the forks followed, the gap before Redis’s reversal, when Salvatore Sanfilippo rejoined Redis, what cloud providers contributed and the drawing’s caption, and removed a count of manifesto signatories we couldn’t source.
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