The fonts are owned and copyrighted by Apple. This is a screen shot of one of the San Francisco fonts from High Sierra. They all have the same notations.

You'll have to ask Apple about using them for your site. The copyright notice, as you can see here, says to refer to the license agreement. From how that reads, I would say maybe (to display and print content). But again, ask Apple to be sure.
E. Fonts. Subject to the terms and conditions of this License, you may use the fonts included with the
Apple Software to display and print content while running the Apple Software; however, you may only
embed fonts in content if that is permitted by the embedding restrictions accompanying the font in
question. These embedding restrictions can be found in the Font Book/Preview/Show Font Info panel.