The player says at the bottom in red "Flash Created By "My Music" Developers in partnership with Musipedia".
This links to http://joshkoo.comp.nus.edu.sg/mymusic/ which is no longer available, but I would guess that's supposed to link to a page indicating "Josh Koo" is the guy that created the player.
The reason it sounds like a piano is probably that it doesn't use your computer's midi patches (which could be very good by the way), but it's using sampled sounds (or generating its sounds without using your computer's midi patches). Quite likely if most midi players you use sound terrible.
There is also a link on the page "If you have an external MIDI piano connected to your computer, please click here to use it". This opens a Java based midi player, although that's not actually working on my browser.