This may be almost too simple to mention, but...
I use a PS/2 splitter with a standard 101 keyboard and normal 2-button mouse, and wanted to use the original i-opener keyboard due to it's smaller size, but I hate the built-in mouse. With the original keyboard plugged into the splitter, neither built-in or external mouse would work.
I opened the keyboard, and used a very small flatblade screwdriver to slide the two rearmost connector pins out of the connector that plugs into the small circuit board. The wires on these two pins are red and gray, and are the mouse clock and data pins. I did not damage anything, and simply slid the pin sockets out of the connector and bent them away. Easily reversable. After testing and reassembly, I now have the original keyboard working just fine with the PS/2 mouse.
I haven't decided yet if I need to relabel any keys, but I did make sure first that I could use CTRL-[ in vi as the escape key. No problem. I won't be too surprised if the original keyboard ends up driving me nuts though. At which point I might give in and buy a small keyboard from the numerous souces cited here.