I guess I never noticed or looked. But Tk4- uses Hercules version 4. The main Hercules page says the current version is hercules-3.07-1. There is a version 4 manual available with an date of November 21, 2015.
HHC01603I version
HHC01413I Hercules version 4.00
HHC01414I (c) Copyright 1999-2012 by Roger Bowler, Jan Jaeger, and others
HHC01415I Built on Jun 23 2016 at 20:32:29
HHC01416I Build information:
HHC01417I Hercules for TK4- (64-bit Linux)
HHC01417I Modes: S/370 ESA/390 z/Arch
HHC01417I Max CPU Engines: 8
HHC01417I Using setresuid() for setting privileges
HHC01417I Using POSIX threads Threading Model
HHC01417I Using Error-Checking Mutex Locking Model
HHC01417I With Dynamic loading support
HHC01417I Using shared libraries
HHC01417I With External GUI support
HHC01417I With IPV6 support
HHC01417I With HTTP Server support
HHC01417I With sqrtl support
HHC01417I With SIGABEND handler
HHC01417I With CCKD BZIP2 support
HHC01417I With HET BZIP2 support
HHC01417I With ZLIB support
HHC01417I With Regular Expressions support
HHC01417I Without Object REXX support
HHC01417I Without Regina REXX support
HHC01417I With Automatic Operator support
HHC01417I With National Language Support
HHC01417I Machine dependent assists: cmpxchg1 cmpxchg4 cmpxchg8
HHC01417I Running on bill-MS-7B79 Linux-5.4.0-77-generic. #86-Ubuntu SMP Thu Jun 17 02:35:03 UTC 2021, x86_
herc =====>