Debian Unstable

Official packages are available at usual mirrors so just:

sudo apt-get install spring
sudo apt-get install springlobby

will give you the latest packaged and uploaded release of spring for debian.

Debians info page for the spring packages can be found here: http://packages.debian.org/sid/spring

Often prebuilt packages for i386 and amd64 on the way to enter unstable could be downloaded from the spring maintainer's alioth account. Use them if an urgent upgrade is needed to play online for example, otherwise please wait unstable mirrors to resync. To download them use:

wget -O- -q http://alioth.debian.org/~mammadori-guest/mammadori-alioth-archive.key | sudo apt-key add -
echo "deb http://alioth.debian.org/~mammadori-guest/ sid main" | sudo tee -a /etc/apt/sources.list > /dev/null
sudo apt-get update
sudo apt-get install spring springlobby