It is becoming more and more difficult to run stand alone servers as so many features now depend on having Active Directory installed. Although most of our Windows servers remain stand alone, we are now running FileMaker Pro and Advanced on AD servers as we're publishing via RemoteApp, which demands AD. We've pleased how this is working.
I don't believe you'll have any problems running FMS on an AD server, but this is subject to how many other services the AD server is managing? If it is a small network and the server isn't also the print server, file server, the top of a forest of a very complex AD, web host, etc. then you should be OK. It is always better to use a dedicated server for FileMaker, but the actual overheads of AD on a small network is relatively small. Do check whether IIS is in use for other purposes first though.
I haven't done this with 15 yet, but have had Server 14 running on my 2012 R2 Domain Controller for over a year now without any problems.
On install the process did halt with an error on one of the required ports, but after a server restart the second install attempt was a breeze.
Hope that helps.