On the twenty-ninth of August, Elastic added the GNU Affero General Public License v3 as an option for the source of Elasticsearch and Kibana, alongside the existing SSPL and Elastic License 2.0. AGPL is an OSI-approved licence, which means Elasticsearch is officially open source again, three and a half years after it stopped being.

Every other licence story I have written about in the last year went the other way. This one is worth recording for the direction alone.

What happened before

In 2021 Elastic moved Elasticsearch and Kibana off Apache 2.0 onto a dual SSPL and Elastic License arrangement, aimed squarely at cloud providers offering the software as a managed service without contributing back. AWS forked the last Apache-licensed release and OpenSearch exists because of it.

That fork is now a mature, separately-governed project with its own users, and it does not un-happen because the upstream licence changed back. Elasticsearch became open source again in August; it did not become the only option again.

What the change actually is

An addition, not a replacement. Users can now choose AGPL, SSPL or ELv2 for the free part of the source, and existing users on either of the previous two are unaffected. Binary distributions do not change.

AGPL is the notable choice because of what it does to the case Elastic was originally arguing about. A permissive licence lets a cloud provider run the software as a service and keep their modifications. AGPL closes that specifically: if you provide the software to users over a network, the source of your version has to be available to them. It is a copyleft answer to the same problem SSPL was written to solve, with the difference that AGPL is a recognised open-source licence with decades of history and SSPL never was.

So the company gets most of what it wanted in 2021, and gets to be open source while doing it. The reason that is available now and was not then is mostly that the argument moved on — the cloud providers built their forks, the competitive landscape settled, and the thing the original licence was defending had already happened.

The part I actually care about

Lucene, and it is the reason none of this ever worried me much.

I wrote a while ago about every string search I did not have to write — analysers, tokenisers, the whole chain that makes chemical names searchable. All of that is Apache Lucene, and Lucene has been Apache 2.0 throughout, governed by the Apache Software Foundation, unaffected by anything Elastic or AWS decided.

Elasticsearch and OpenSearch are both distributed systems wrapped around Lucene. The licence fights were about the wrapper. The part that does the searching — the inverted index, the analysis chain, the scoring — was never in play, which is why a fork was viable at all and why the two projects remain as similar as they are.

That is the durable lesson from watching three of these in a year. The question is not just whether a dependency's licence could change. It is where the irreplaceable part actually sits, and whether that part is governed by someone with a reason to change its terms. A project owned by a company that needs to make money from it is in a different position from one held by a foundation, and knowing which is which tells you more than reading either licence.

What I would do about it

If you are on OpenSearch, nothing. It works, it is Apache 2.0, and switching back for licence reasons alone would be a migration paid for with no functional return.

If you avoided Elasticsearch since 2021 on licence grounds, that objection is gone and it is worth re-evaluating on the merits — which now means comparing two genuinely diverged projects rather than one project and its recent copy. Three and a half years is long enough for the feature sets, the operational behaviour, and the managed-service options to differ in ways that matter more than the licence ever did.

And if you are starting something new, the useful change is that the choice is back to being a technical one. Which is the whole point of a licence being uncontroversial: it stops being a factor, and you get to decide on the software.