Yeah HD couldn't beat the Japs so started outsourcing suspension components in the 80's to Showa, which may be owned by Honda.
There were two primary providers of suspension units to the various Jap makers, Showa and Kayaba. The Sportster fork is as good as any of the basic Jap suspensions and the aftermarket companies, Progressive, Traxxion, Race Tech all make upgrade kits for them so they're easily and readily modified