Chevereto main release (3.X) is commercial software and you need a license key to install and use Chevereto 3 in your server. All Chevereto licenses share the exact same system functionalities and the only difference is how many domains are allowed per license type.
The license key is automatically included when you download any paid release. You can find the actual license key string in your client panel.
Core license is the basic Chevereto license that will grant you permission to run Chevereto in one domain at production environment. If you need to install the system on your local machine or on a test server you are also free to do it. If you need to run more websites you can upgrade the Core license to Network.
Network license grants you permission to use Chevereto in more than one domain at production environment. This means that you are allowed to install and run the system in in several domains (different websites) at the same time.
The latest free version is Chevereto Free which has been forked from V3 and is totally free to use. Chevereto 1.X and 2.X are Open Source and free which means that you don't need to purchase it to have permission to use it. There are extremely limited features in these free versions and is not the same as the last version (3.X) as you may notice in this comparison table.