I have yet to verify the Following - But I will post it here for someone else to research.
*** This procedure involves editing a game file; create a backup
copy of the file before proceeding. Certain game retailers are
releasing a bonus Freedom Force disc. This disc will give you more
powers as well as 3 new recruitable built in characters for
campaign mode. They are Blackbird, Iron Ox, and Supercollider. Use
the following steps to unlock them without the bonus disc. Use a
text editor to edit the "init.py" file in the game folder. Add the
following lines to the file:
APP_ENABLE_XTRACHARS = 1
Now I know that Blackbird, Iron Ox, and Supercollider come with gogs version of the game. I just do not remember if they are available during the campain. I do however know that the init.py file is included with GoG's version, but does not contain the above lines. Notepad can be used to edit the init.py file.
The instructions say to add those lines, so where you've said the GOG version doesn't have those lines, that sounds normal as you need to add them. Try it and let us know. (I'd do so myself but I don't own the game yet).