I run Netatalk in a Debian virtual machine on Windows. Works with 10.9 all the way down to System 6.

If you scroll down the Classic Mac Networking page to the Netatalk section you'll find all the info you need to get it set up.

In the first link you mention, in the table of compatible OS's, in the section for lion and mountain lion, there's a link to an apple KB that describes how to enable conectivity to legacy AFP services. However, it seems mavericks is out of the question. I would like to mention my favorite software to transfer files between all families of OS's: Timbuktu. Version 6.0.3 (last one to run under OS9) is perfectly compatible with the current version (8.8.5).

I have heard that copying the AppleFileServer.app (or whatever it is called) from 10.4 and copying it into 10.7 works, or might. I have yet to try it out, but it sounds interesting.

You can also run Windows 2000/2003 Server, either on a real machine or a VM, although I haven't tried it in a VM. The SFM feature actually does work fairly well.

From your existing hardware base, you can use the 10.3 or 10.4 system as a central server and everything else connects to it as a client. AFP will work perfectly fine in this situation.

After several sleepless nights regarding this I FINALLY cracked it. I have a Mac Mini running Mavericks Server and an iMac i7 running Mavericks in the studio. I need to somehow transfer files between them and my Pro Tools machine, a PowerMac G4 MDD running Mac OS 9.2.2. After trying ShareWay IP, DAVE and spoofing AFP versions without any luck I stumbled upon MacNFS.

MacNFS is an awesome implementation of NFS for Mac OS 7.6 to 9.2.2. What it does is giving Mac OS the same way of mounting NFS mounts as we are used to with AppleTalk and AFP, via the chooser.

What you need is:

*MacNFS on your "Classic" machine
You can find it here: http://download.cnet.com/Thursby-MacNFS/3000-2651_4-5269.html
It says in the "read me" file that you need the full version of MacNFS in order to use the updated version in the archive, but you don't. Just drop the file named "MacNFS" in your extensions folder and reboot. Now, if you go to the Apple menu and open the chooser, you should have an icon named MacNFS. Goodie. Click it and it asks for a serial number. Serials can be found in the usual places, or you could use this one:
td56-s9pm-wocp-42m9-ezpr-c

*NFS Manager on your OSX/Intel machine
You can find it here: http://www.bresink.com/osx/NFSManager.html
No need for a serial if you can live with the nag screens (you will only need the app when you manage your shares anyway. The NFS server always starts up with OSX).
OSX already has NFS implemented, since it's a UNIX based operating system (and NFS is the default file sharing protocol in any UNIX based OS). What NFS Manager does is giving you a nice and Macish GUI for the command line NFS stuff. What you need to do now is add a NFS share and set some access rights.
This is pretty straight forward.

Next you mount your newly created NFS share on your old "Classic" Mac system, and off you go with your filesharing awesomeness!

Thought I'd share this with everyone since it seems to be a big issue over all since apple "killed" AFP for us.

EDIT: Added the app and the guide along with a screenshot here:
MacGarden/MacNFS 3.0p3

Edit: Made the app link clickable - IIGS User