As there are some drastic changes between versions, it would be helpful to have two different versions running of Bibledit.
This is possible, but not recommended for production work, as they will be overwriting each other's configuration.
Do it this way.
Install the newer version according to the instructions.
When installing the older version, do this:
./configure --prefix=/home/joe/older make sudo make install
Then to run the older version, type this:
/home/joe/older/bin/bibledit
Joe stands for the user's name.