skype will be enabled either way. Skype is running at both ends, it already knows the capabilities of your contacts (that's how it updates their status on your n900j. I don't know the inner workings of its proprietary protocol but I imagine that when you go online on n900 skype, all of your skype contacts are refreshed according to what the skype client they are currently logged into reports as their current (hardware, O/S, skype version) capabilities. try with wifi (or to a laptop on your own LAN) to get the hang of it.