If you're building your own blender binaries from the svn, here are the instructions for making them work with the addon:
- edit file source/blender/python/intern/bpy_rna.c
- locate where 'is_readonly' is defined (around line 5336 but this may vary depending on the version)
- force it to 0
- rebuild your blender
I tried this on 34648M from svn and it worked like a charm, although I didn't invesigate for side effects.
Another trick could be to undefine USE_PEDANTIC_WRITE, but I've not tested this one.
I'm in touch with blender developpers to see how the issues I'm having can be addressed until callback are available.