Larian Studios Forums Divinity - Original Sin Divinity - Original Sin - General some techn. questions about the mp mode

During the last two campaign videos sven mentioned that it is "now possible" to play together with a Mac or Win version of the game. He highlight this in a way, as if this is a real technical problem to solve.

I know there comes problems, if you use special MR Frameworks like Game spy, MS Play for matchmaking and other infrastructure task, but where comes the problems from, while providing cross-plattform multi play in dos?

Is this caused by the different game versions (resulting in different byte-structures: for example 32/64 bit).

Or more precisely: will all platforms be able to play together and exchange savegames, mods and so on...

I don't know if the issues were compatibility itself, or just getting the Mac game engine caught up enough that the Mac version of the game was feature compatible with the Windows version.

For compatibility Larian did say different language versions shouldn't be a problem, but I don't recall any other conformations for different releases (Steam with non-Steam, etc), other than the intent is to have all version be compatible.

I also unable to find any confirmations. So some technical background would be nice. Maybe this could be covered by a developer.