Just a quick update on the status of my projects. The Qalculate! plasmoid is now included in the KDE SC (>=4.5), so development will continue on KDE trunk. I have modified the standard calculator runner, adding support to libqalculate. It will be available starting from next version (KDE SC>=4.6). By the way, since some months I am also part of the Qalculate project. I am mostly working on bug fixing.
Cirkuit is still being developed, expect a new release in the near future!