the source here: http://www.koreaherald.com/view.php?ud=20190517000378
and the relevant point: "Before the government-wide adoption, the ministry said it would test if the system could be run on private networked devices without security risks and if compatibility could be achieved with existing websites and software which have been built to run on Windows.
Note that "compatibility with Windows" as a requirement is never something that goes 100% well. Expect surprises along the way.
Here is a more recent source (translated from Korean) - note that the figures are improperly translated, check the source article for the right numbers: https://translate.google.com/translate?hl=&sl=ko&tl=en&u=https%3A%2F%2Fnews.v.daum.net%2Fv%2F20200204150508999
Recently, the handling of online defamation has become a hot topic on many mass media as well as social media channels. News Article for Reference: https://www.jiji.com/sp/article?k=2020052500387 In response to these reports, it is expected that lawsuits and disclosure requests will become more publicly known; and government agencies will order stricter enforcement in addition to tightening regulations. However, under the current state of Japan, we will not be able to handle the increase of such administrative burdens and will have trouble dealing with it appropriately. Thus, we have decided to stop providing our service on mstdn.jp and mastodon.cloud starting June 30, 2020. We are very sorry for the inconvenience and appreciate your understanding on the matter.