It's a free personal edition. It isn't a trial version or a demo. It is a fully usable personal web server with no limitations, no nag screens, no spyware, and no advertisements.

Abyss Web Server is a compact web server available for Windows, Mac OS X, and Linux operating systems. Despite its small footprint, it supports HTTP/1.1, secure SSL/TLS connections (HTTPS), on-the-fly HTTP compression, dynamic content generation through CGI/FastCGI scripts, ISAPI extensions, native ASP.NET support, extended Side Includes (XSSI), custom error pages, password protection, IP address control, anti-leeching, and bandwidth throttling.

It also features an automatic antihacking system as well as a multilingual remote web management interface that makes its configuration as easy as browsing a web site. It is an easy to use and feature-rich software.