The last time I played, you had to declare war and attack, to keep a race from colonizing in your space. Is that still the case?
Yes, there is no treaty that prevents the AI from colonizing in your area of influence. Although this would be a great feature either to put into the game at game start or add as a diplomacy option I haven't heard of this being included. I though would be all for it.
Also, the AI got mad when you colonized planets, but it continues to colonize as many as it wants. Is that still the case?
I've never had a problem with it. However, personally I just ignore the AI unless I really see them as a threat.
edit: nevermind, wrong game! I was thinking of Star Drive II... haven't played that one in a long time either....
I answered your questions either way 
have a good day
