Support for releases is subject to the availability of community and volunteer resources to effect that support. Generally this will include the current release and prior releases for which there is a sufficiently large community of folks still running a particular release in production.
Implementers are encouraged to deploy Sakai release tags or source or binary artifacts. A number of schools use maintenance branch code in production in order to pick up bug fixes as they become available. The project teams providing fixes provide a minimal level of testing, however, a great deal of community QA is achieved for each fix by relying on the local QA processes of organizations preparing the fixes for deployment to production. (See the Release Practice Guidelines for further information on how and what goes into these branches.)