To lock licenses we need a criteria to recognize the computer. If the criteria match the code entered during installation the software runs otherwise it stays in evaluation mode. 

What you mean by "can it be downloaded on multiple ones within a location and just not used at the same time" is a network license or network floating license.

The four classical ways to do it are:

• A physical dongle placed on the parallel port or USB. We do that but it requires an extra cost and shipment. drawback people may loose it, advantage you can move it around.
• The Ethernet board ID. The Ethernet Board is the place where you enter the socket for the network. They have a universal unique ID called MAC Address. Almost every computer have now an Ethernet board and this is a cheap solution to lock software. Drawback is that you need to change the code whenever a customer upgrade his computer. Nothing to do with a network license although we use a network device.
• The SolidEdge license ID or CAD ID. Since all users will have a valid SolidEdge license we base the code on it. Best solution but not yet available for SolidEdge. Should be OK in January. One of the benefit is that if the SolidEdge license is a network floating license our license becomes network as well. Which is good. When this solution will be available with SE15 we will migrate for free most of the customers to it.
• A more complex solution requiring a more complex setup. We don't use this because our software should remain flexible and easy to setup. Such solutions are used by Microsoft for windows XP. Unfortunately we are not Microsoft :)

 This is the help on our web site:

http://www.radialsoft.com/paiement/ProtectionHelp.asp.php