It may be that more than one thing is being called "green ghost".
I used to have a male pastel who's father was a hypo mojave from TSK's "extreme hypo" line. Now I see TSK calling that founder female ghost "green ghost" in their online linage for any of their hypo mojaves. I had heard that others had already proven TSK's ghost compatible with the lager group when in 2009 I bred that pastel het TSK ghost (green/extreme) with a possible het ghost female from whatever Brian Sharp was selling years ago (I think it was called "yellow") and producing this:
Also, I seem to remember a post once by NERD explaining the origin of one of the other lines (don't remember if orange, yellow, or butterscotch) and I understood them to be saying the other line was selectively bred starting with what they described as a green ghost. I don't have any info to report on incompatible green ghost lines but seems I've recently read that report in forums.