A 'neutral' is supposed to remain in its home system, yes. Whether that is hard coded or not I can't say. Maybe the 'personality group' in the ai_settings file controls this? All of the neutrals are personality group 0 while the AI empires have other numbers for their personality group. But the 'neutrals' do NOT always remain in their home systems. It's better than it used to be. I occasionally had neutrals taking over the galaxy in some earlier betas.
Now, I think it's mainly the "space anomaly" event that sometimes boots a neutral ship out into the galaxy.
[This message has been edited by Baron Munchausen (edited 10 March 2001).]