Epicor has a license type for that called, unironically, a Web Service license. There are some limits on the frequency you call it though. Otherwise, people would buy just one license and run all of Kinetic through it. 
In User Account entry, you can create an Integration Account for this. Create a Scope and associate it with an API-KEY and the Integration Account checkbox gets checked (or you have to check it, don’t recall). Play around with that instead of using a person’s credentials - which is not good for…reasons.