As of August 2013, the download links for Pax Galaxia on the official Dio Games site have gone down.
Therefore, I have elected to host them on this server.
Please note that I am not affiliated in any way with Dio Games or Diodor Bitan. Diodor Bitan reserves all rights and ownership of Pax Galaxia. Furthermore, these links are for the free, "demo" version only. To purchase the full version, you should consult diogames.com.
You can download the Mac version here.
This version contains the interface mod which is detailed on the customization page. It also fixes a crash that occurs on later Mac OS versions when switching to fullscreen, by using an updated version of the SDL framework.
As of October 2018, the diogames.com domain has gone down, rendering the multiplayer lobby for Pax Galaxia inoperative. Since the actual web hosting for the lobby servers remains online, I was able to modify the Pax executable to connect to my domain instead, which then redirects to the actual diogames.com web host. When that inevitably expires in the future, it would theoretically be possible to reconstruct the actual lobby PHP files, and in that case, this modified Pax executable would continue to operate without any further download. Anyway, currently you can join online games, although I don't think you can host any at the moment. You can download the modified executable here (Mac only at present). You can also join in on recreating the lobby PHP files on GitHub here.
The Windows version is available here.