To run uDig:

1. Open the net.refractions.udig plug-in
2. Double click on the file 'udig.product'
3. Under the testing section near the bottom left of the editor, press the "Synchronize" button.
4. Below that, press "Launch the Product" to run uDig.
5. On Ubuntu 8.04 after installing the Firefox 3 rc1 update, install the package xulrunner or xulrunner-gnome-support. The command in the latter case is

   apt-get install xulrunner-gnome-support

   .