If I brought it for one machine with my Apple ID, do I buy it again for the other?

simayi said:

As title.

I had an iMac and a Macbook Air, if I brought Lion for my iMac in App with my Apple ID. Do I need to re-purchase it again for my Macbook Air?

Click to expand...

No. You can install it on up to ten Macs with the same Apple ID.

Compare this to a single Ultimate license for Windows 7 that will set you back about $220.

As long as you use the same account you can install it on another Mac.