Drivers passing through San Francisco have a new roadside distraction to consider: billboards calling out businesses that don't cough up for the open source code that they use.

The signs are the work of the Open Source Pledge - a group that launched earlier this month. It asks businesses that make use of open source code to pledge $2,000 per developer to support projects that develop the code. So far, 25 companies have signed up - but project co-founder Chad Whitacre wants bigger firms to pay their dues, too.

Whitacre, whose day job is head of open source at app-monitoring biz Sentry, told The Register his employer has for three years operated a scheme to pay developers who maintain and upgrade open source code.

"We do dollars per developer, the thinking being it's the developers and software engineers on the staff at a company who benefit the most from open source, who become more productive because of open source," he said.

"I had one conversation with a representative from a larger firm and he's like: 'Chad, you're asking me to spend ten million on maintainers.'"

Whitacre affirmed that request, and pointed out the firm "spends ten million on something anyway."

The issue of paying FOSS developers is neatly illustrated by Randall Munroe's classic xkcd 2347 comic titled Dependency that highlights how key software can often be maintained by a single individual - who is worthy of support, given the extent of reliance on their work.

Some businesses - such as US retailer Target - have started financing open source development along the same lines as the pledge program, and the Indian online exchange Zerodha has pledged $1 million a year to support open source programs.

The Open Source Pledge team wants more businesses to do likewise.

"These billboards are obviously a cheeky way to get people's attention, and they're working," Whitacre told us. "I am hopeful that, if we are persistent, five years from now Microsoft will join, Google will join, and Facebook will join."

But Whitacre admits that outcome will take time. Most of the firms signing up at present tend to be smaller startups - maybe on series B and C funding rounds.

"We're starting with this beach head, with this very focused approach," Whitacre told us.

"We'll grow together with all the FOSS foundations, with the ecosystem, with the maintainers. It's going to be something we pursue together in the coming years. But, yeah, I would say I am hopeful that with persistence and time this will work." ®