Adding Multiple Licenses to a Single Gateway
In order to better support our community of third-party module authors, we also allow for multiple license keys to be installed on a single Gateway. A third-party module author can issue a license key for their module directly to a customer, whereby, they can immediately do an install of the module. To learn more, check out the Third-Party Module Showcase to find and purchase modules that extend Ignition's functionality.
It is important to note that there may only be one license on it with a platform version per Gateway. The platform will look similar to the picture below. If you try and activate a second license with a platform onto a Gateway that already has a license with a platform, the new license will overwrite the previous license.
In the image below, two licenses have been applied to this Gateway, but only one is active.

Effective vs Applied Licenses
This page has two sections, which detail different information.
Applied Licenses shows all licenses that have been applied to the gateway. Entries here are typically purchased or given, and have a license key associated with them.
Effective Licenses provides a summary of modules active on the gateway. Modules are active if they're provided by an applied license. This area is the result of potentially multiple licenses across various activation mechanisms. For example, if license A provides module A, and license B provides module B, then Effective Licenses would show that both modules A and B are active on the gateway. The caveat here is that the modules will only appear if they're installed on the Gateway. In this same scenario with licenses A and B, if module B was not installed, then it will not appear under Effective Licenses.
In addition, the Effective Licenses area may have "synthetic" items that are translated to modules. For example, in the case of Edge gateways, their Applied Licenses will show products. These products will be translated to modules under the Effective License section.