Can you run OSX as a server without OSX Server.app? I have just set-up a new Hackintosh server running ML (10.8.4) but I have been unable to get a redeem code for the OSX Server.app from the Apple Developer site (some temporary problem).

However do I really need it?

My definition of "server" is: web server, file server (SMB, AFP), sshd, git server.

Does OSX Server.app provide additional server components or is it simply a UI frontend to the config files?  I seem to be able to start sshd and apache without the Server app and have been doing UNIX admin long enough not to be scared of config files, so I'm thinking I can get the server running without it.

Can anyone advise?
For the uses you need, you can do it with base OS X.

OS X server adds stuff like Time Machine support on networked drives, networked spotlight, Open Directory, policy support, etc.  

They're useful features, but you don't really need them for the stuff you're describing.