Like SIDizer, this plugin suffers from "hung" notes when used with the sustain pedal. The operation of the sustain pedal in Oresus means that it is impossible to play live. This is further complicated by the voice stealing algorithm when maximum polyphony is reached. (v1.2)
These issues were reported to Hypersynth back in May 2014, and while their support is fast and friendly, they are either unwilling or unable to resolve this rather fundamental problem, claiming the fault lies with modules of MIDI code they have "no access to." They did supply a beta to test with some adjustments but this behaved very strangely - when releasing the sustain pedal, all notes held by hand were released as well.
Again, I am putting this in the "unfinished" category.
One guesses that the underlying fault is shared code between both plugins. Solving the problem in this plugin should in theory create a patch to solve the SIDizer plugin as well.
I can only encourage Hypersynth to solve the issue, and complete an otherwise promising product.