Even if you have an old Macintosh you should still be able to install and run Blockland version 20. My old iMac that my brother uses to play is about 5 years old and still runs Blockland without a hiccup.
Nope, I'm running 10.4.11 on a PowerBook G4
Regardless of the OS version, you should still be able to play. Can you please shed some light on to why you can not play the current version of Blockland?
Apple has made it impossible for a single app to run on both 10.4 and 10.6 therefore you must fork over the money to upgrade. You signed on for this bullstuff when you bought a Macintosh.
If you installed v19, it would auto update to v20.