At the core of most open-source project sites were centralized
management systems (SCM) such as CVS and later on
Subversion. At the
same time a new breed of SCMs was emerging, called
decentralized) version (or revision) control system
The core idea of DVCS is that rather than having a
central, canonical source tree, you have a system of multiple
working copies. This means that multiple developers can collaborate on a
project even if they are but sporadically connected.
The interactions between these distributed working copies is a
bit reminiscent of the interactions between personae in social networks.
Therefore project hosting sites naturally grew up around concepts of
DVCS with social features in concordance with the code-sharing model.
Some of the most popular DVCS at present are Mercurial, Git, and Bazaar,
and each has a closely associated, well-known service, respectively BitBucket , GitHub, and Launchpad.
On top of these source code repositories global open source teams are then creating projects using highly productive languages like Ruby on Rails, Python, Node.js, Sinatra , PHP, Pearl (Yes Pearl is still alive and kicking) and even C, C++ and of course Objective C
The key concept behind this global code explosion is forking, taking one open source project, forking it and continuing along a new branch, towards a new goal. This is highly reminiscent of the Cambrian Explosion 530 million years ago, when a plethora of new life forms appeared within a comparatively speaking very short time.
IBM's BigInsights, which is based on Apache Hadoop, as well as IBM's Watson which makes use of Apache's UIMA-technology show the influence of open source on a global scale.