Here on openCollabNet we publish a graph that shows the adoption of Subversion on public Apache servers (actually: only those servers that report their mod_dav_svn module, Subversion). The raw data is published monthly by the Canadian security and on-line services consulting company E-Soft.
Last month Subversion reached 150,000 servers that report their Subversion module and the growth is spectacular. In August 2006 E-Soft reported 46,000 servers, a year over year growth of over 3x !!! From 2005 to 2006: same story, from 15,000 to 46,000.
The number only reflects a subset of the Subversion servers out there. There are lots of Apache servers that do not report their modules (I understand it is practice to no longer do so for security reasons). And then there are the instances of public Subversion servers that run svnserve and many more servers behind firewalls. So, the report shows the trend of the adoption of Subversion, the actual number is much higher.
Another interesting report to look at is from CIA.vc (not the government). This report covers commit messages of over 1,000 open source projects. Subversion blows all other systems away and it is clear that it has overtaken CVS by a stretch, at least according to this report.
How many developers using Subversion does this translate into? Of course it is impossible to give an absolute number but if you take an average of 5 developers on each of these servers that E-Soft reports, make an adjustment for other public servers, add some hard data on really big projects that we know about (like the Apache project), add the number of developers using Subversion as part of CollabNet’s platforms (we have hard data on that of course), add hosting services and make an estimate of corporate use, then it is fair to say that well over 2 million developers now use Subversion.
Subversion is unstoppable and certainly one of the most successful open source projects.