my point is that they don't have a common API (scripting and add-ons comment) at the moment.  and if they aren't in the same language, the programming teams couldn't share code (might not be able to even they were).  a common API at this point wouldn't really matter, would it?  because a common API would only mean new things might be shared.  it wouldn't mean (for example) that D|S could acquire cloth dynamics from Poser and Poser could get D|S's GI or SSS.  a  shared API would only work if it were based on common capabilities. 

i guess on the off chance that the common capabilities were actually the complete source of a capability particular to one or the other, you might be able to share existing features.  but i'm not sure there's even a single capability like that.  hence my statement about not being sure it's possible without re-writing one or the other.

but maybe i'm missing something.