>Any chance this is going to run on non M$ platforms?
I discuss this briefly here.http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1270494815
Summary is: Chance -- yes. Soon? Not so much but it iwll happen.
>there are some way to add some sort of resistor somewhere?
VBB models circuits at the function block level. You need something like SPICE if you want to design at resister level. However as you can see modelling at the function block level is easier and in many ways more powerful.. more on that soon.
>For example: how can I recognize the cathode/anode of a LED component?
Well the LED component has a property to expose the cathode if it is used otherwise it is assumed to be connected to ground by default. However the point is valid and you may have to change the way you look at a circuit a little to make best use of VBB as a software development tool.