Yes, it actually looks like an older version than the one included in Jaguar.
Any of us under the NDA, with access to Panther, has the right to demand a copy of the source code of the new Chess, because of the conditions of the GPL (under which GNUchess, and, because of the "viral" aspect, Apple's Chess, are distributed). Further, anyone with that source (or even the binary) can redistribute it.
So anyone with a copy of Panther (legally, of course) can get the source from Apple, or post the source or binary. Unless I'm severely mistaken about some aspect of the GPL, and I find that unlikely since I've read the whole thing several times.
Yes, I just read it (and it turns out it's under its own GNUchess License, which predates the GPL- this is ancient!) and Apple must give the source to anyone who asks, as long as they also legally obtained the binary.