React Particals in blender 2.5

I was wondering if react particals are in blender 2.5?
I have been looking for them for ages.

I have seen something called partical insance is this anythng to do with reactor particals?

No Particle Instance is a modifier already present in 2.49.

Reactor are mentionned in the TODOS:

A new branch dedicated to particles has been recently created.