I'm working on my Mac today, which means you get a Mac tip!
You might remember that when we first released AutoCAD LT for Mac, it was available only on the Mac App store.
With the 2013 release, though, you have choices. You can still get AutoCAD LT for Mac on the App Store, OR you can buy a license from your favorite local or online reseller. The serial number accompanying this purchase can be used to activate AutoCAD LT 2013 on a Windows machine or a Mac (or on a Mac running Windows...the possibilities are endless).
So what's the difference between the App Store version and the serialized version? Feature-wise, absolutely nothing. On the logistics side, there are a couple of differences. The App Store version of AutoCAD LT cannot be upgraded or put on Subscription. (It can, however, be used on multiple machines with the same Apple ID per Apple's license agreement.) In the serialized version, you'll also see a Subscription item in the Menu Bar.
This provides direct links to the Subscription Center, support reuqests, and downloads -- all accessibile if you have a subscription.
I hope that helps clear up any questions you might have had about the two purchase options.