EPPlus is licensed under a dual license model. Polyform Noncommercial 1.0.0 for noncommercial use and Commercial Licenses for commercial businesses.

The Commercial Licenses are licensed per developer, have unlimited deployment locations and are divided into two categories:

Subscriptions.
With a subscription you can always use the latest version, but you need to have an active license as long as you use EPPlus for development. To continue to use the software you will need to renew your subscription at the end of the current subscription term. Subscriptions are available for 1 or 2 Years.

Perpetual Licenses.
With a perpetual license there is a period during which you can upgrade to new versions and have access to support. You can then continue to build software against the versions that were released during the this period without having to renew the license. You can receive Upgrades and Support for 1 or 2 years, after which you can choose to renew or continue to use the version installed during your Upgrade/Support period.
Packages of perpetual licenses are available for various sized teams. The License covers developers within the same organization.