From the website:
Unreal Software is a small and independent game- and software developer. I (Peter Schauss) use this name to publish my hobby projects.
Most of these projects are games. The greatest successes of Unreal Software are "Stranded (I+II)" and "Counter-Strike 2D".
The name "Unreal Software" has actually no distinctive meaning but therefore allows a lot of interpretation. However it is definitively not related with the "Unreal" games and engines by Epic Games.