Subversion has been used in basically each and every open source project as a replacement for the previously most used CVS.

Subversion was better tjan cvs, but still bad in many aspects, slow synchronization and bad branching and merging support come to my mind.

Because of these shortcomings and because of the idea of decentralized versioning coming up, many systems like git, mercurial, and others came up then, and git seems to be the most successful of these by now