When you create a branch from a tag you will have to change the version and a url in the pom files.
Simply add another level to the version number.
The tag 3.1.7 for example was branched and was given the version number: 220.127.116.11.
Additionally you can change the url where documentation is written from
Now when you do a mvn site-deploy, it won't override the existing documentation.
For every technology change you will probably have to create a branch from the trunk.
The trunk of jxpfw now uses j2ee7 for example.
Before we switch the trunk to support j2ee8, we have to create a branch that we may call j2ee7.
The version in this branch can remain the same but we do have to increase the version in the trunk now.
As of this writing the trunk uses 3.2.x so this should be changed to 3.3.0
Additionally you will have to change the url in the branch from scp://shell.sourceforge.net/home/project-web/jxpfw/htdocs/ to scp://shell.sourceforge.net/home/project-web/jxpfw/htdocs/j2ee7
Finally you may want to have a look at the site's documentation. The index.xhtml page for example may contain information about a certain branch. When info about the branch is deployed as well you may want to update the index.xhtml page as well. Additionally you may want to change the example tags in the release-non-snapshot.xhtml page.