This issue prompted me to go back and check the contents of our Ubuntu installers, and unsurprisingly, there's a disparity between the 32 bit and 64 bit version - the plugin tersus.appserver.ui is missing from the latter.
To fix this. you can try installing this plugin manually by downloading tersus.appserver.ui_1.3.45.tgz, and extracting it as root to /usr/share/tersus/eclipse/plugins/tersus.appserver.ui_1.3.45
If that fails to solve the problem, you'll need to perform a cross platform (manual) installation, or if you have a 32-bit version of Ubuntu at your disposal, download and install the 32 bit installer from the download page.
Sorry for the inconvenience.
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