I have the Nikon > Micro Four Thirds Speed Booster now and have been testing it for a few days, so check back for a review next week. Lovely with the Samyang 85mm F1.4 on the GH3. The adapter also has a built in aperture control ring for Nikon G lenses which works very well, though would be nice to see a declicked version.
My personal opinion is that this green flare is not created by the nikkor. It's a stretched flare, and sphericals mostly produce round ones, like these.
http://i2.wp.com/ferradans.files.wordpress.com/2013/07/mg_1331.jpg
Of course, I might be wrong too. hahahaha :)
Have you tested a similar camera setup with a different taking lens?