unlikely - a couple things that took 32bits of space on 32bit chips, take 64bits.,namely long integers and pointers. memory addresses may only be 40 or 48 bits, and the compiler may optimize for this.
proably 33% more RAM is a more typical figure..
Some people are using it on real servers - I am not.
I'm working on a rewrite at git://github.com/ry/ebb.git. I'll have a
release, which will be 0.3, in the next week or so.