Thanks for your response. An open data license does not automatically mean that the data can be imported into OSM. For example, what about the attribution requirement for Seoul Open Data Plaza?

If my research is correct, the following page is relevant for you: https://data.seoul.go.kr/etc/accessTerms.do

I'm not a licensing expert, but I believe the data from the Seoul portal should not have been used in this way, as it may constitute a copyright violation?