Reality Software has created a few games, the most well known of which are the Death Match series. The games were removed from circulation for a time, but re-released in 2018 as unsupported.
This was a multiplayer game set in the world of Death Match Project Alpha. It was originally released in client form to be played on a central server, but versions of that server were made available for download.
This package is widely considered to be unstable, including by the developer, and is entirely unsupported. When (not if) you encounter issues, you are on your own. For best results, a Linux system with significant system resources is recommended.