Ethereum co-founder Vitalik Buterin said he is rethinking his long-held preference for permissive software licenses, advocating for broader use of “copyleft” frameworks as open source enters what he described as a more competitive and concentrated era.
In a blog post published on July 7, Buterin explained that permissive licenses such as MIT or CC0 have historically been his choice because they allow anyone to use, modify, and redistribute code with minimal restrictions, facilitating wider adoption.
In contrast, copyleft licenses like GPL or CC-BY-SA require derivative works to be shared under the same terms, including the publication of source code, creating a legal safeguard for openness.
Buterin wrote:
“Historically, I was a fan of the permissive approach. More recently, I am warming up to the copyleft approach.”
The Ethereum co-founder has been much more active in recent months, proposing new ideas and conducting research amid a shift in priorities.
Protecting openness
Buterin said his earlier preference stemmed from two core beliefs: first, that permissive licenses reduced friction for enterprises hesitant to share their own work and second, philosophical opposition to copyright and intellectual property laws.
He said that permissive licensing is the closest practical approach to “no copyright at all,” aligning with his belief that sharing data or ideas should never be seen as theft.
However, he now sees three major factors changing this calculus. The first is that open source has become mainstream across industries, with companies such as Google, Microsoft, and Huawei not only using but also publishing significant projects under open licenses.
In such an environment, copyleft requirements are less of a barrier and can actively sustain openness by ensuring that large firms share improvements back with the community.
The second factor is the changing culture within the crypto industry itself. Buterin described the space as increasingly “competitive and mercenary,” with fewer projects open-sourcing their code purely out of ideology or goodwill.
In this context, permissive licensing alone is insufficient, and he argued that legal requirements under copyleft are needed to ensure shared progress.
Economic arguments for a concentrated world
The third factor driving Buterin’s shift is rooted in economic theory. Drawing on ideas from radical markets economist Glen Weyl, he argued that in industries with superlinear returns to scale, strict property rights lead to a concentration of power.
He explained that if one actor has twice the resources of another and can produce more than twice the output, the gap compounds over time, resulting in monopolies.
Buterin warned that these conditions, combined with rapid technological progress and geopolitical instability, threaten to create persistent and self-reinforcing power imbalances between companies and countries.
He noted that some governments have responded with policies to enforce the diffusion of technology, such as EU standardization mandates, China’s technology transfer rules, and the recent U.S. ban on non-compete agreements.
Buterin argued that copyleft achieves similar diffusion goals in a neutral, decentralized way, without favoring particular actors or requiring top-down enforcement, describing it as a “broad-based and neutral way of incentivizing diffusion.”
He said:
“Copyleft creates a large pool of code (or other creative products) that you can only legally use if you are willing to share the source code of anything you build on it.”
Buterin acknowledged that permissive licenses still make sense when universal adoption is the primary goal and are a valuable component of property rights.
However, he urged developers to recognize that the benefits of copyleft are “much greater today than they were 15 years ago” and that open source communities should seriously consider copyleft as a mechanism to prevent excessive concentration of power and ensure that technological progress remains accessible to all.
His comments come as the AI and blockchain development communities are actively debating licensing models amid concerns that foundational innovations risk being captured by a small group of dominant players.
