The impetus behind the branding clarification seems to be this HN thread [1]. For more history, see the the debut announcement [2] and its corresponding HN thread [3].
[1] https://news.ycombinator.com/item?id=18929709#18930413 [2] https://drewdevault.com/2018/11/15/sr.ht-general-availabilit... [3] https://news.ycombinator.com/item?id=18458908