Grab the program and place it in an appropriate directory such as /usr/local/bin. Then add (or create) a .procmailrc file to add a rule which looks like:
:0 fbw
* ^To:.*@egroups.com
| /usr/local/bin/egroups
You may need to do something to get procmail to recognize this file, but on current Linux systems, the above step is all you need.
You can pick up the entire archive for version v0.02. This contains all of the files mentioned on this page.
Once you have the tar file, you will need to extract and build it. Do something like the following:
cd mkdir egroups tar xvfz egroups-0.02.tar.gz cd egroups-0.02 make su make install