I just got Beyond Compare 3.0.2 for Linux to run on 64-bit Kubuntu 8.04.1. It is pretty painful to setup.
Here are the steps: 1. Install 32-bit compatibility library. Using the graphical package manager, install the package "ia32-libs". You can also install from a terminal using the command "sudo apt-get install ia32-libs".
2. Install 32-bit version of QT3. (On older versions of Kubuntu/Ubuntu, you may be able to install the package "ia32-libs-kde", this package isn't available for Kubuntu 8.04.1 AMD64)