I wonder if Apple still delivers new version of safari for PowerPC-based macs. On that computer, I'm stuck with firefox 3.6.28. Is Safari still updated on PPC system updates?
Safari for leopard has been discontinued. If you are looking for a browser that is currently receiving updates TenFourFox is a fork of firefox that is updated along side the primary version, but remains compatible with PowerPC cpu's.
While Safari 5.0.6 is the last version for 10.5, newer versions of the webkit framework can be obtained from the leopard-webkit project https://code.google.com/p/leopard-webkit/ . Webkit based applications can use the newer framework to provide updated rendering.