Jaguar may not be able to run the absolute most current version of Safari, which would explain why you're not finding any updates for it. The latest mention I've found of Safari for Jaguar is 1.0.3, and that's from over 2 years ago.
Yeah, with 10.3 (Panther) Apple released Safari 1.3, but only for that system, and then with 10.4 (Tiger), they released Safari 2.0, but again, only for the new system software. I've been wondering why that is? Are they afraid people won't pay to upgrade to the latest system or is there really something in the new browser versions that can't be backported to the older system relatively easy?