MacOS – Process ‘storeagent’ eating bandwidth

Yes

You can simply copy the application to your Applications folder, and then login to the Mac Application Store with the same username and password. This will validate the application and allow you to run it without needing to download it again.

The only time this will become a legal issue is if you are copying it to someone else's computer, however, they will not get updates for the application unless they log in as you, or otherwise, unless they also have a purchased copy of the application.

You can also read my answer here for a more detailed explanation of Application installs on the Mac and the Mac App Store.

If you are running Yosemite, then you can enable Family Sharing so that others can download the same app purchased by you.