Tried it out. It's still very buggy. Several times it wouldn't let me make a legal move. But is a good start. Hopefully they will continue developing it.
S-chess website

Gary,
"They" is me. It's a project I work on when I have time, but I hope to keep improving it. I fixed a bug this morning that was causing some moves to result in an error - it may have been what you were encountering. I welcome reports of specific problems; if I can track down the problems I will fix them.
Kevin Leuthold

Gary,
"They" is me. It's a project I work on when I have time, but I hope to keep improving it. I fixed a bug this morning that was causing some moves to result in an error - it may have been what you were encountering. I welcome reports of specific problems; if I can track down the problems I will fix them.
Kevin Leuthold
Wow, so you're the guy behind that app page.

One can also play Seirawan Chess online and via e-mail, here:
http://www.chessvariants.org/index/msdisplay.php?itemid=MPseirawanchess_
The following new website is very impressive and is useful for playing Seirawan chess by correspondence: http://seirawanchess.appspot.com/