"POP 4" which extended mail receiving protocol POP 3

It seems that POP 4 adds some new expansion set to existing POP 3, but this is one thing.

Details are as follows.
Post Office Protocol Version 4.
http://www.pop4.org/

I feel that IMAP 4 and others are better, but I wonder if the idea like POP 4 like this is better.

Software which is supposed to be able to use this POP 4 once exists.

O3 Mail System.
http://www.pop4.org/o3/o3.html