CGoban is the name of a set of computer programs written by William Shubert: CGoban (or CGoban 1), CGoban 2 and CGoban 3. All of them are SGF editors and clients for playing go on-line, but there are important differences between them. For help for the Kiseido-client search sensei's titles for the term 'KGS'.
There is a potential for ambiguity because the names of the programs are so similar. "CGoban" without a version number usually refers to the first program, which was developed to be a client for Unix and X11 machines to connect to servers with protocols similar to that of IGS. CGoban2 and CGoban3, while full SGF editors and readers, are clients only for KGS. Also, while CGoban is a C program, CGoban 2 and CGoban 3 are written in Java.
One of the few things that CGoban and CGoban2 have (had?) in common is the use of "Bill's fluorescent green denim" - a green and black striped pattern that he used for background. While professional UI gurus would probably sneer at it, I found it refreshingly idiosyncratic. Recent releases of CGoban2 have had less and less of it; I wonder if Kiseido is exerting editorial control. John Aspinall