The GPL version 2 has been in decline for some time, and has just dipped below a 50 percent adoption rate among open-source projects, according to new data released by Black Duck Software.
While some of this decline may be due to GPL version 3's increased adoption, at least some may derive from growing commercial interest in Apache-style licensing.
One of the best indications of this shift is Red Hat's decision to license the JBoss HornetQ project under an Apache license, rather than the Lesser General Public License, to which it had previously defaulted.
Having said that, it's important to note that Apache's share of the market hasn't been growing dramatically (see the July 2009 data), which lends further weight to a hypothesis that GPLv3 is cannibalizing GPLv2. Even so, I find the dip interesting, and anecdotally I'm seeing a groundswell of support for Apache.
This isn't to suggest that the GPL doesn't matter: it clearly does. As Redmonk analyst Stephen O'Grady recently noted, "the GPLv2 is more popular than all of the other licenses on the (Black Duck) list...combined."
But as Open Core becomes the default business model for "pure-play" open-source companies, we will see more software licensed under the Apache license.
The GPL makes sense in a world where vendors hope to exercise control over their communities (by constraining the sorts of derivative works that remain palatable to would-be competitors or "free-riding" users), but if the desire is to foster unfettered growth, Apache licensing offers a better path.
I don't see an end to GPL adoption anytime soon, as its ethos appeals to a certain class of developer and because it can offer tangible development and business benefits, as I'll be arguing at Monday's "Which open-source license is best?" discussion with the Free and Open Source Software Learning Centre. The whole Apache vs. GPL debate may be much like Coke vs. Pepsi: a matter of personal preference and nothing more.
With GPLv2 adoption dropping below 50 percent of open-source projects surveyed by Black Duck Software, however, it's very possible that preferences are starting to shift in favor of Apache licensing.
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