JTDX is a piece of software which is based-on and similar to WSJT-X but it has different features and may have a performance boost over WSJT-X in the FT8 mode on HF.
The following is from the “About” tab on the JTDX website.
What is JTDX?
JTDX means “JT,T10 and FT8 modes for DXing”, it is being developed with main focus on the sensitivity and decoding efficiency, both, in overcrowded and half empty HF band conditions.
It is modified WSJT-X software forked from WSJT-X r6462.
JTDX supports JT9, JT65, T10 and FT8 © digital modes for HF amateur radio communication, focused on DXing and being shaped by community of DXers.
© 2016-2017 by Igor Chernikov, UA3DJY and Arvo Järve ES1JA
It is created with contributions from DK7UY, DO1IP, ES4RLH,G7OED, MM0HVU, RA4UDC, SV1IYF, UA3ALE, US-E-12, VE3NEA, VK3AMA, VK6KXW, VK7YUM and LY3BG family: Vytas and Rimas Kudelis.
JTDX is licensed under the terms of Version3 of the GNU General Public License (GPL)
The algorithms, source code, look-and-feel of WSJT-X and related programs, and protocol specifications for the modes FSK441, FT8, JT4, JT6M, JT9, JT65, JTMS, QRA64, ISCAT, and MSK144 are Copyright © 2001-2017 by one or more of the following authors:
Joseph Taylor, K1JT; Bill Somerville, G4WJS; Steven Franke, K9AN; Nico Palermo, IV3NWV;
Greg Beam, KI7MT; Michael Black, W9MDB; Edson Pereira, PY2SDR; Philip Karn, KA9Q;
and other members of the WSJT Development Group.
JTSDK by Greg Beam, Joe Taylor
[Check out the JTDX website for links to download variations of the program.]