The term branch off or branch off date is used by release engineers and release managers of OOo. With this term they want to identify the date when the release code-line is split from the general developer code-line (see the picture). Until the branch off features, enhancements and general integrations can be done on the development code-line. But it is important to finish all implementations until this date. This means that the respective CWSs with the features, enhancements and general integrations must be integrated before the branch off. On the release code-line only stopper and blocker issues are excepted. Further builds/milestones will stabilize the code-line until the final release. General development is then going on with development code-line (DEV300).
When is the branch off?
The date for the branch off will be announced on the wiki page for the corresponding release. E.g. OOo 3.2 release.