I have read through the specs and believe this to be the case but wished for a confirmation on this. FMS 13 is compatible with Mavericks (10.9.x) but is not compatible with Mavericks Server.
I have been running FMSA 12 on ML Server with no problems but have been unable to get the preview of 13 to run on Mavericks Server. Seems that the admin console will not load. Making administration of the server impossible.
I am not sure of how I can “Uninstall” the server portion of Mavericks without erasing and starting over. This is something that I am not willing to do at the moment. I am hoping that this is not a permanent restriction and will be corrected soon. If not we may be looking for another solution.