Paintball 2.0 (Alpha build 41 Full Linux x86 Standalone) is working well on 64bit Ubuntu desktop 14.04!
In the hope it helps others - here is what I had to do:
Note: The multi-architecture method of using packages with the :i386 suffix was I think introduced in => Ubuntu 13.10.
1) Add the 32bit arcitecture and common librarys
sudo dpkg --add-architecture i386
sudo apt-get update
sudo apt-get install libc6:i386 libncurses5:i386 libstdc++6:i386
2) Add the 32bit video librarys
sudo apt-get install libdrm-dev:i386
sudo apt-get install libX11-dev:i386
sudo apt-get install libXext-dev:i386
sudo apt-get install libXxf86vm-dev:i386
sudo apt-get install libjpeg62:i386 (note: libjpeg-dev:i386 not used due to conflicts)
sudo apt-get install libpng12-0:i386 (note: libpng12-dev:i386 not used due to conflicts)
sudo apt-get install libgcrypt-dev:i386
sudo apt-get install libgl1-mesa-dev:i386
3) Add the 32bit sound librarys:
sudo apt-get install libsdl1.2debian:i386 (note: libsdl1.2-dev:i386 not used due to conflicts)
sudo apt-get install libasound2-dev:i386
sudo apt-get install libasound2-plugins:i386
4) Ensure permission to write to the Paintball2/pball/configs/ folder and the Paintball2/pball/maps folder.
5) Ensure setting the game to use ALSA as the sound driver (best option if no OSS).
Add or update the following in Paintball2/pball/configs/config.cfg
(Create this file if Paintball2 had not previously successfully been started)
seta snd_driver "alsa"
6) Run the game. no command options necessary.
First time running the game took a long while to start and write/rewrite the config.cfg files etc.
After that it was very quick to load.
Note1: OSS sound (seta snd_driver "oss") is not natively supported in Ubuntu 10.10 <> 15.04.
The following post indicates it might be available in 15.10https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1434842
It will not work with pulseaudio:i386 oss wrapper (padsp) as it doesnt support trigger or mmap
It will not work with alsa-oss:i386 oss wrapper (aoss) as it also does not support mmap
Note2: SDL sound (seta snd_driver "sdl") works with the aoss wrapper.
However this seems a secondary option as it randomly crashes on startup.
Note3: (edit) Just noticed that the following 32bit librarys listed on the Paintball2 download page were already installed on my system and so are likley to also be required.
sudo apt-get install libgpg-error:i386
sudo apt-get install libxau-dev:i386
sudo apt-get install libxdamage-dev:i386
sudo apt-get install libxdmcp-dev:i386
sudo apt-get install libxfixes-dev:i386
Note4: (edit) Also just noticed that the following 32bit librarys listed on the Paintball2 download page do not seem to be installed at all on my computer and so may not be required.
Please reply if it was helpful for you or if you can add some information about success or modifications required for other 64bit Linux versions.