check-if-email-exists's source code is provided under a dual license model.
If you want to use check-if-email-exists to develop commercial sites, tools, and applications, the Commercial License is the appropriate license. With this option, your source code is kept proprietary. Purchase an check-if-email-exists Commercial License at https://reacher.email/pricing.
If you are creating an open source application under a license compatible with the GNU Affero GPL license v3, you may use check-if-email-exists under the terms of the AGPL-3.0.
Read more about Reacher's license.