Under this family of licences, Sullivan places the GPL, the Affero GPL and LGPL.
Sullivan presented his findings in a talk he gave at FOSDEM recently, titled "Is copyleft being framed?"
While not mentioning the company specifically, figures issued by Black Duck Software, which are used by quite a few writers to claim that use of the GPL is falling, were not used by Sullivan.
He had his reasons for doing so. "Some of the most common licensing numbers used are published by a company who does not share their methodology. That's not science. FLOSSmole is an interesting project to generate the data in a verifiable way."
He pointed out that even studies that claim GPL use is declining say the absolute numbers of both GPL and non-GPL free software are increasing. "The FSF is pleased to see the growth in free software either way," he added.
Sullivan said a number of factors needed to be considered when looking at licensing and trying to gauge the rise or fall of any particular type. "Are we counting all free software projects on the web? Active projects? Small projects? Mobile applications? Lines of code or all individual programs treated equally? Packages with multiple licences?"
He said he chose the Debian project because it is a mature distribution that serves as the basis for many others, including gNewSense and Trisquel. He said he was citing the information he had garnered about Debian to raise the level of the community conversation about the issue and ask people to more closely examine the assumptions/framing behind all of this data.
"I would not expect the results to be significantly diffrent for other distributions, except for those that might include more proprietary software. Additionally, software is vetted before entering Debian, so we know there are no duplicates," Sullivan said.
Sullivan's counting was based on symlinks to shared licence familes, as well as regular expression matching, using standard Debian tools.
He started with Sarge, which was released in 2005, before version 3 of the GPL was released. He found a total of 15,195 packages of which 10,730, or 71%, were licensed under the GPL family.
The next release Etch was in April 2007. There were 18,043 packages of which 13.872 or 77% were under the GPL family. This was an increase of 6% as far as the GPL family went with a rise of 18% in the total number of packages in the distribution.
Lenny, the first Debian release after the GPLv3 was published, was released in February 2009; there were 21,994 packages and 19,218 were licensed under the GPL family. The number of packages showed an increase of 22% while the GPL percentage rose by 10%. Another statistic of note was 630 packages which were under the GPLv3 or LGPLv3 by name.
The last Debian release, Squeeze, which emerged in February 2011, had 28,126 packages of which 26,271, representing 93%, were under the GPL family. And showing an increase of 400% were GPLv3 and LGPLv3 packages which now totalled 3154.
Sullivan concluded that debate about use of the GPL family of licences was being framed.
He advised that one should pay close attention to counting methods. "When it comes to looking at a different, well-vetted frame of software — like what's in Debian GNU/Linux — GPL family use is very high."
He added: "Either way, don't overstate the popularity of licenses (sic) as proxy for organizational (sic) influence/success, whether for the FSF, Mozilla, Apache, or any others.
"Don't forget that the license (sic) and law are just tools to achieve the end. Instead of popularity, look at progress toward the goals, even if that progress has to be qualified as tenuous. Don't forget that non-copyleft free software is still free software."