Now more than ever, the development of the Linux kernel is a matter for the professionals, as unpaid volunteer contributions to the project reached their lowest recorded levels in the latest “Who Writes Linux” report, which was released today.

According to the report, which is compiled by the Linux Foundation, just 11.8% of kernel development last year was done by unpaid volunteers – a 19% downturn from the 2012 figure of 14.6%. The foundation says that the downward trend in volunteer contributions has been present for years.

+ ALSO ON NETWORK WORLD: Ex-FCC attorney says Internet plan won’t achieve broadband goals | Java vs. Node.js: An epic battle for developer mind share +

CC 3.0 SA\Wikimedia\LinuxMag.com

Even so, unpaid contributors were still the single biggest source of commits in the latest Who Writes Linux, at 11,968 total changes – good for 12.4% of the whole. However, corporate contributors collectively account for much, much more. The Linux Foundation said that more than 80% of all work on the kernel is done by paid professional developers.

According to Linus Torvalds, the shift towards paid developers hasn’t changed much about kernel development on its own.

“I think one reason it hasn't changed things all that much is that it's not so much ‘unpaid volunteers are going away’ as ‘people who start writing kernel code get hired really quickly,’” he told Network World.

Torvalds said that, while Linux development has changed for plenty of other reasons – and that, naturally, new contributors pop up all the time – many of the original developers, with decades of experience, have simply been snapped up by companies with an interest in Linux.

“We may have started as volunteers, but we're happily employed doing Linux these days,” he said.

Torvalds’ own role in development has become increasingly hands-off, according to the report – he has personally signed off on 329 patches since version 3.10 of kernel was released, or 0.4%. Increasingly, subsystem maintainers do their own reviews and merges of code.