AI’s Billion-Dollar Copyright Battle Starts With a Font Designer

Matthew Butterick was intrigued—but disturbed—when he first sat at his computer to play with an early version of an artificial intelligence programming tool called Copilot.

The tool let him start typing a line of code and then filled in the rest, like autocomplete for programmers. But Butterick, a prominent figure in the programming community, also recognized Copilot was “trained” on billions of lines of open-source code, including his own, without permission.

Open-source programming, a pillar of the tech world, encourages developers to freely distribute their code and let others build on it. The catch: Those who reuse and modify code ...