OneWire is a new feature of .NET Micro Framework 4.2, but it's a bit too big to fit in the current flash sectors.
We're currently evaluating a "special build" which would reduce the available code space a little bit, but which would add in the OneWire feature.
I look forward for the onewire implementation too. It was a horrible surprise the NotSupportedException beeing thrown .
One remark: We use NotSupportedException to let the programmer know, that this functionality never ever will be implemented, or it does not give any logical sense to implement it. In cases, where it is already not finished, but it should be, we use NotImplementedException instead.
One question: Why didn't you suppose, the .net.mf will be extended in the future, so the additional code space will be needed? Isn't it a problem already in version 4.2 with insufficient code space? What are the options to solve the space problems?