According to ICANN registration records, pianostreet.com domain was registered January 8, 2003. The site might exist under a different name before that though.
In the "About/AboutPS" tab of this forum:
"Op 111 Productions develops and provides innovative IT products and services for musicians.
Current projects include Piano Street (
www.pianostreet.com), a discussion board (formerly Piano Forum) and sheet music resource for professional pianists, piano teachers and piano students."
The bottom portion of each page of this website has:
"Copyright © Op 111 Productions, 2001-2023. All rights reserved."
So it looks like 2001 is the starting year.
BTW: I would bet that op. 111 is in reference to Beethoven's last piano sonata.as opposed to Brahms string quintet #2 or some other composer's op. 111.