You have to use GameRanger on the PC and Mac to have online multiplayer. You also need to be running the 141 final patch on the PC. LAN mode is also supported Mac<->PC. This is true for all Mac versions, DVD, App Store or other download stores.
App Store aside we have our own DRM which is simple and does not have any hidden copy protection applications or services installed. You install the game then activate the game online. That's it! From then on you can play the game as much as you want offline or online without any DRM services or "phone home" systems getting in the way.
As someone who helped design the Feral DRM I can tell you it was designed using the thought "What would I think if I was a customer?". It took a while but but sticking to that rule meant we ended up with a user friendly DRM that stays out of the way while keeping the pirate horde under control. 😀
Edwin