Release numbers will generally follow the scheme major.Ddelta
``major'' releases differ considerably in architecture and potentially break backwards-compatibility to versions with a different major version number, particularly with respect to scripts and plugins. Therefore, they will occur only very infrequently. Usually, a major version change also means that a very important milestone has been reached.
``delta'' refers to the actual point release. This may skip a number, if some problem is found in between committing the files to the repository (which entails that the code builds, and that regression tests pass) and the release of the files through the SourceForge file release system.
The release number uniquely identifies the code used to build the release, which is useful for tracking down obscure bugs, but dependent software versions are not recorded.
There may be a need in the future to release development versions of the software (aka beta releases), in which case the release number will be used major.minor.Ddelta. Otherwise development software will basically be managed using the SourceForge subversion repository.