liquidfun 1.1.0 (new formula)

LiquidFun is a 2D rigid-body and fluid simulation C++ library for games
based upon Box2D.
It provides support for procedural animation of physical bodies to make
objects move and interact in realistic ways.
> Is it possible to make this use an existing copy of box2d, so it doesn't need to conflict?

Now I'm sure it isn't possible.

I compared both library.
liquidfun doesn't change box2d interfaces but change internal part (cpp source).
So it's not possible to just compile using existing box2d.

I googling and find many "use case" such as this (for example cocos2d framework's users):
You use box2d. 
Suddenly realise you need liquid simulation. 
Replace box2d with liquidfun and get it!
You don't need to re-write other code just need to recompile. 
There is no ability to roll back from box2d to liquidfun.