From the soruceforge.net project entry:
ShowEQ or SEQ for short is a program designed to decode the EverQuest data stream and display that information on another computer running the Linux OS.
ShowEQ was originally a project started by the Ethernalquest team as a way to better understand the EQ packet structure. It's since turned into one of the most active open source projects on sourceforge (99.5902% activity rating) and quite an interesting environment has developed around it.
Features as of version 3.0a include mapping of the current zone including player's line of sight, entity locations and information, and an experience calculation system. It's designed to be run on any machine capable of running X Windows, and has been compiled (and run) on Linux, FreeBSD, and SunOS to name a few. It's only true limitation is it's reliance on a closed-source binary, libEQ.a, which is used for decryption of the packet stream.
Many have asked why the software isn't readily available for Windows, more useful, or more accessable. Oddly enough, after every release of a Win32 equivilant the encryption scheme on vital packets has been changed by Verant - which indicates to most that they don't mind it being an exclusively Linux project, or that they don't see it as a direct problem or threat to their game's integrity.