We’re following SemVer (as much as one can be following it when the major version is 0). At this point bumps of the minor (second) version number are considered major releases and always include new features or significant changes to existing features. API compatibility between major releases is not a (big) concern (although we try to break the API rarely and only for a good reason).
The development cycle for the next major release starts immediately after the previous one has been shipped. Bugfix/point releases (if any) address only serious bugs and never contain new features.
Here are a few examples:
0.5.0 - Feature release
0.5.1 - Bug-fix release
0.5.2 - Bug-fix release
0.6.0 - Feature release
CIDER and cider-nrepl are released independently, but follow the same release policy overall. CIDER contains references to the cider-nrepl version it supports and would normally inject the newest cider-nrepl version possible.