Licensing for development or staging sites

When you purchase the plugin you'll get 1 license key that can be activated for 1 site (unless you've purchased a specific multi-site plan). This license key is intended to be activated on the live domain.

For any development or staging sites you could simply leave the license key field blank. The plugin will still function as expected.

Depending on the subdomain structure (staging.* or dev.* for example), you might be able to activate it there "for free", but it's not required to use the plugin.