BOOPSI coexists perfectly with GadTools. Take Prefs/Palette (of WB 3.1) as an example. It mixes a GadTools GUI with external colorwheel and gradientslider BOOPSI gadgets.
I don't think you are allowed to distribute ReAction. And ReAction is OS 3.5+ only. You might want to have a look on ClassAct, the predecessor of ReAction. It's available on Aminet. There are only very few things which work with ReAction but not with ClassAct.
