Our current policy is to support the most recent major version (currently 3.X), and previous major versions for a minimum of 1 year after each one has been superseded. This period has already elapsed for 2.X, as 3.0 was released on Sep 17, 2014.
Event Store docs are hosted on GitHub. The repository is public and it’s open to issues and pull requests. Contributions, corrections and feedback are all welcome.