It gets a little confusing because ESTA(which South Koreans are eligible for) is valid for both tourist and business use, and is a visa waiver.
As this comment[1] states with an official source:
> A B-1 visa may be granted to specialized workers going to the United States to install, service, or repair commercial or industrial equipment or machinery purchased from a company outside of the United States, or to train U.S. workers to perform such services.
Maybe the business use of ESTA also covers the above use cases?
