There is a lot of discussion by unhappy players on the Steam Discussions for SpellForce 3 Reforced. Seems that spyware was incorporated along with a necessary login...meaing that you have to be online to play the game. I wonder if the GOG version has these problems.

This is already discussed here. Yes, it also have it - as dll files. It not needed to play offline\online, and you can delete those dll files keeping folders and probably keep gog folder (needed only if you want add it to Galaxy after offline installation, which one is not available at this time anyway).

You should have SpellForce 3 Legacy in Library with 1.40.1 without those dll files and avialbe as offline installer.