Remember that the code is now looked after by Symbian Foundation, not Symbian and that this is a completely different company. We (Symbian Foundation) were donated the code by Nokia, Sony Ericsson and NTT DoCoMo.
We are a not for profit, under a limited by guarantee structure (i.e. no shareholders).
Nokia themselves seem to have "got" open source, having donated us the code and also opened up Qt far more (which incidentally allows us to put Qt on the phone which is currently in beta)