How's that open source licensing coming along? That well, huh?

When a vendor and a community stop loving each other, things can get very forked up

State Of Open Multiple license changes have rocked the open source community over the last few years. For vendors concerned, the impact has ranged from business as usual to potentially catastrophic.

Dr Dawn Foster, director of data science at the CHAOSS Project, presented research at this month's State Of Open Con '25 in London, showing what had happened to three projects – HashiCorp's Terraform, Redis, and Elasticsearch – after their licenses were changed. All three made the tweaks due to what Foster called "pressure from investors to increase profitability."

In all three cases, the license changes led to forks in the code. Terraform begat OpenTofu; a fork of Elasticsearch became OpenSearch; and from Redis came the Valkey fork. 

A 'victim of its own success'

The Register spoke to the founder and former CEO of Percona, Peter Zaitsev, about the licensing issue.

According to Zaitsev, the definition of open source was being eroded in pursuit of monetization. "Open source became big, and now in a lot of cases, it's a victim of its own success," he said.

Zaitsev foresees increased polarization of open source. "I think people understand that the open source license is not enough."

Zaitsev also highlighted the need for contributions to a given project to be from multiple sources, to ensure that if one group did not wish to contribute anymore, the health of the project would be assured: "The project is much stronger than any company."

The CHAOSS project is all about better understanding open source community health and, in the three examples of forks arising from license changes, Foster's research looked initially at repo activity: commits, additions, deletions, contributors, and so on. Foster noted that more metrics could be used, but "this is really just a start."

However, it also shows what can happen when a vendor changes a license, particularly if that vendor is relying on community contributions.

In the case of Elasticsearch and HashiCorp, relicensing didn't dramatically impact contributors since most of the contributions were internal – neither had much of a community contributing to the core product.

However, according to Foster, "there was a pretty big impact on some users of Elasticsearch, who had to decide whether they could use it." One result of the decision to adopt a more restrictive license was Amazon forking the project in the form of OpenSearch.

Foster compared Elasticsearch from a year before the relicense to a year after. The result? Not a lot of change in contributions, since more than 90 percent of contributors were Elasticsearch employees. Similarly, Amazon's fork was mainly worked on by Amazon employees until the project was brought under the umbrella of the Linux Foundation. The move has resulted in more non-Amazon employees contributing.

Terraform was similar to Elasticsearch in that the vast majority of contributions to the project came from one company: HashiCorp. However, unlike OpenSearch, the fork of Terraform – OpenTofu – was under a foundation from the start rather than a company, meaning that contributors came from a diverse range of companies, including Red Hat, from the beginning.

Foster noted that none of OpenTofu's contributors had previously contributed to Terraform.

This was not the case with Valkey, a fork of the Redis project where a significant number of contributors had also contributed to Redis. After the Redis license change, many switched to Valkey with the result that contributions from non-employees dwindled.

The takeaway is that forks from relicensing tend to have more organizational diversity than the original projects. In addition, projects that lean on a community of contributors run the risk of that community going elsewhere when relicensing occurs.

"Projects with greater organizational diversity tend to be more sustainable over time," Foster said. As time passes, the impact of the license changes will become clearer. Foster concluded: "It remains to be seen over the longer term if these types of forks might actually become more sustainable than the original projects if any of these vendors continue to struggle to meet the expectations of their investors." ®