Yes, FlowRepository is released as open source under the GNU Affero General Public License. You should be able to find a snapshot of some older source codes under Source Forge. So far, we have not received many request from developers who would be willing to obtain the sources and therefore, we do not invest our efforts into updating the Source Forge snapshot very often. Therefore, if you wish to receive the newest snapshot of our production branch, please let us know and we will build an updated one for you.
Please be aware that proper installation and deployment are somewhat tricky, mostly due to resolving various JRuby dependencies and general configuration related issues, and our resources for supporting third parties setting up their own servers are very limited. We do have a guide describing the server side installation but you still need technical skills and experience with hosting of web based applications in order to troubleshoot and set it up properly on your own. The installation_docs/FlowRepository.Server.Installation.Instructions.pdf within the FlowRepository tar.gz should get you started in terms of setting up the server.