OK, quick first impressions:
I’m using Blender 2.8 64bit on windows 7 Pro 64bit, using your new .py file and connecting to oscistudio v5.5 64bit.
1_ good: immediately connected to oscistudio, and oscistudio immediately saw the simple mesh I created. It seemed snappy w.r.t. reaction to blender. It also reflected simple edits, translations, scale, rotation, etc.
2_ bad: oscistudio did NOT preview the blender animation timeline while scrubbing in blender. I did a simple animation changing translation and rotation of the mesh, but the objects did not move in oscistudio.
3_good: oscistudio DID see the rotation/translation animation when I used the “send animation” button in blender.
4_bad: oscistudio did NOT honor hide/show visibility toggle. All blender objects were visible in oscistudio, even if they were invisible in blender.
5_good: oscistudio seemed to handle blender modifiers and high vertex counts correctly, for the few I tested.
This is not comprehensive, just about :20 of testing simple things.
SO>> not quite done, but not fully broken either.