We have covered all kinds of interesting hacks here in the past. Installing Linux on your old or new e-readers is not impossible. You just need to know a bit of hacking to get started. MarekGibek @ MobileRead already has released what you need to install Debian Linux on your Kobo device. This seems to work on Kobo Mini and Kobo Touch devices.
This is not a perfect hack, so there are some shortcomings. You shouldn’t use your main reader for experiments like this. The developer is hoping to enable better screen updates, multitouch, and screen rotation in the future.