Up to 2 physical machines.  If you have a laptop and desktop, work machine and home machine or a similar combination, this is a valid licensing scenario.  You may run more than one instance of RightEdge on each machine as well.

A receipt of the transaction which includes line item detail of your order should be emailed to you.  This will also contain your license key.  If for some reason you did not receive this email, click on the "My Account" link along the top of the site, and click "Order History".  You'll see your order number, which is clickable and to the far right is a PDF link which contains a copy of your receipt.

Click on the "My Account" link along the top of the site, and click "Order History".  You'll see your order number, click that order number.  Click the "Show Serial Number" link to display your serial number.

See this link for details.