Well Tiger was last updated with a major update in 2009, two years newer than the most recent Entourage update. I also love PPC. I have multiple PPC Macs in near-daily and I'm typing one one now. I too love doing as much as possible on these older machines, but for anything that involves the potential transfer of personal info (email, online banking, etc.) I am content to use my MacBook and maintain compatibility with modern security protocols and certificates and encryption algorithms. I totally get where you're coming from and, in a perfect world, I would love to be able to use only my PPC machines. Sadly that isn't possible though.
That's pretty cool that you're a dev on Classilla, I look forward to the next update