Which compression algorithm(s) is KGB based on? How does it differ from the competitors?
WinAce is known to use LZSS, WinRAR seems to use PPM, MS-Cabinet calls its LZ variant "LZX". For 7-zip or UHA it is obvious, they use LZ-Markov or PPM variants with selectable dictionary sizes (7-zip also supports BZip2).
According to the amount of RAM KGB uses, I would guess that there is some LZ-Markov variant used as well. The CVS repository can not be browsed at the moment, so I can not read the sources to check this myself.
Unfortunately, KGB seems to ignore file attributes under Windows ("Hidden" or "System" files are not at all added, Read-Only or Archive attributes and file dates not restored), and the file header is quite inefficient IMHO. Therefore it is not useful for archiving purposes.
It obviously uses PAQ6. See 2 lines below.
"How does it differ from the competitors?"
It does NOT work.
"The CVS repository can not be browsed at the moment, so I can not read the sources to check this myself."
Download the linux source.
The windows source is compressed with KGB (what
an excellent idea !!!), so I can download it but
not read it since the great EXE thing does not work.