In order to compile Gambas on GhostBSD, you must install required development packages.

For this How-to we use pre-compiled packages, but you can use GhostBSD ports instead.

Here is the packages list install command for GhostBSD 20.11.28: (On 30/Dec/2020)

# sudo pkg install autoconf automake gettext dbus gcc alure libtool libffi bzip2 unixODBC mysql57-client sqlite3 libXtst cairo ncurses gsl openssl imlib imlib2 curl pcre poppler gmime26 gtk3 qt5 sdl sdl2 sdl_ttf sdl_mixer sdl_image sdl2_ttf sdl2_mixer sdl2_image glib libGLU gmime26 glew gtkglext libv4l v4l_compat libxml2 libxslt pkgconf

Get the source code and change to its directory.

$ git clone depth=1
$ cd gambas

At present there are a few patches need to be applied to the makefiles and one .c file to compile on BSD.
I (Bruce Steers) have created a fork of the main gambas master branch that auto-updates any new changes with the patches applied.

Clone it to a folder names bsd-gambas with this command..
$ git clone --depth=1 --single-branch --branch master-bsd bsd-gambas

Then, you can compile the Gambas source code:

$ ./reconf-all
$ ./configure -C --disable-qt4
$ make
# sudo make install