The approach taken with the Harmattan program at Nokia was rather simple, since it happened along the MeeGo project. All the pieces that Nokia wanted to share were contributed in the context of MeeGo or Qt, most of them while they were being developed. For all the rest Nokia had a strong business reason to keep it Nokia proprietary (and then there were the usual binaries from third parties).

A lot of Harmattan proprietary UI code happens to be written as / for MeeGo Touch Framework, which is currently unmaintained since all the development went for Qt Quick.

Whatever is closed between Qt and Kernel is probably either a delicate piece or a component unique of Harmattan, not developed further and with an OSS alternative at MeeGo upstream.

What do you want opened and why? Maybe there is an alternative solution. The Mer project and people here like timoph or Stskeeps know that path very well.