Wintin.Net's Terminal is based on Putty, a free Telnet client written and maintained by Simon Tatham.
The Windowing System
The Windowing System uses a free version of the Magic library, from Crownwood Consulting. This has more recently become a commericial package.
The Addin Infrastructure
The addin architecture, and much of the underlying structure of Wintin itself, is based on infrastructure developed for SharpDevelop, an open source IDE for .Net languages.
The Chat Client
The Chat Client uses code from the MudMaster 2000 Codebase, written by Kevin Cook.
MCCP protocol support is based on work by Oliver Jowett, and uses the amazing zlib dll written by Greg Roelofs and Jean-Loup Gailly.
MXP protocol support uses the MXP Library, written by Tomas Mecir.
The Original Idea
The original idea for Wintin, and the foundation of the script language, came from Tintin++, developed by Bill Reiss, Joann Ellsworth, Jeremy Jack and David Wagner and subsequently ported to Windows as Wintin 95 by William Lees, the author of Wintin.Net.