All products on this site, free, or otherwise, have a software license. It is not permitted for you to redistribute or sell any product from this site without the express permission of the Author.
Where a license key is required for a product, this is normally retrieved by the product itself and stored in your product settings, under the licensing section. This key will likely be tied to your PC hardware, but in general, you can install most of the products on a minimum of 2 PCs (to allow for mobile use, etc.).