Share iPhone Apps Between iPhones

Here's how you can install the same (paid) application on two different Mac's with different Apple ID's.

Step 1: On the first Mac, find the iPhone App in iTunes, select it, and hit Cmd-R to reveal it in Finder.

Step 2: Transfer the .ipa file in Finder to the second Mac.

Step 3: On the second Mac, open iTunes, go to the Store menu and select "Authorize Computer…".

Step 4: Enter in the email address and password for the first Mac's Apple ID.

Step 5: Open the .ipa files from earlier and install them on your iPhone.

It's that simple!