Ideally, we'll move the entire source tree over to a Maven structure in one big bang. As this move is very tricky and time-consuming, we should have a subversion branch in which we can practice.
The subversion branch should contain barely any source code, but should reference the source in trunk instead. Subversion externals can be used to create these references. This way, the code itself isn't duplicated, which prevents a fork (which will undoubtedly prove to be hard to merge when the time comes).
The new branch should be added to Bamboo, to be build automatically. The build should be triggered by both a change to the branch, as well as a change to the original code.
The branch in the Subversion repository that is used to develop the Maven project structure is this: http://svn.igniterealtime.org/svn/repos/openfire/branches/maven-externalsbased
Changes to that location are used as a trigger to execute the following build plan in Bamboo: http://bamboo.igniterealtime.org/browse/OPENFIRE-MAVENEXTERNALS
This build plan is a child of the Continuous Integration build plan of Openfire (trunk). This causes a new build to be started when a change is applied to trunk.