Hi, I managed to upgrade an Old Qube 3 :), the process is simple, I bought the Strongbolt Linux(USD55) wich is better quality and support, it is based on several other OpenSource projects.

My Sun Cobalt Qube 3 (Qubito :) ) is now Upgraded and flashed it EPROM, now it supports Kernel 2.6.

Strongbolt is really nice, it installs BlueQuartz, hope that project will not die soon.

Here is a Picture from "Qubito".