...It is an enhanced edition of the excellent WSJT-X software by Joe Taylor K1JT, Steve Franke K9AN, Bill Somerville G4WJS, myself and others (https://sourceforge.net/projects/wsjt/) that provides several additional features and improvements, as well as more frequent updates and bug fixes.
Notes: wsjt-x_improved is experimental and is licensed under GNU GPL v3 (https://www.gnu.org/licenses/gpl-3.0.txt). I am not aware of any adverse effects. However, use it at your own risk!
Subscribe to the mailing list: https://sourceforge.net/projects/wsjt-x-improved/lists/wsjt-x-improved-community.
Find the various installation packages on the "Files" tab (https://sourceforge.net/projects/wsjt-x-improved/files/).