When creating a custom application using the API, the number of available user licenses for the Blackbaud product should be taken into consideration.
Yes, the API uses a single user license to connect to the related database. Multiple instances of the same custom application will still only use one API user license. Third-party applications or custom applications can use the API to connect. When initializing the API connection you can enter a user name and password as parameters, or you can have the login screen displayed where the user must enter a user name and password to proceed.
For Blackbaud Technology Partners seeking a method to initialize the API in an API license free mode so that it does require the client to purchase and unlock the API module, please review the following article.