Have these patches been submitted upstream? If so, can we
add a link to a web page tracking upstreaming progress,
such that we can determine when 'jdtx-hamlib' can be removed
in favour of 'hamlib'?

I don't think those patches are submitted upstream. I checked diff between jtdx-hamlib's master with commit 954d70c143a9a0293371d8def3a7300ce3ca68c4, which has quite some differences. I am not a developer of either package, so I cannot tell which one/ones is necessary. As it turns out, the configure options seem a lot different from the official one. The following is in the README of jtdx-hamlib:

$ ../src/configure --prefix=$HOME/hamlib-prefix
--disable-shared --enable-static
--without-cxx-binding --disable-winradio
CFLAGS="-g -O2 -fdata-sections -ffunction-sections"
LDFLAGS="-Wl,--gc-sections"

While in hamlib and wsjtx-hamlib, the build configuration is:

(arguments
     `(#:configure-flags '("--disable-static"
                           "--with-lua-binding"
                           "--with-python-binding"
                           "--with-tcl-binding"
                           "--with-xml-support")))

Given that it is a fork, doesn't the home page, synopsis and
description need to be tweaked?

Why define and not define-public?

I basically followed the existing package wsjtx-hamlib.