I did a rough count of possible people from IMDb and other sources, and it hovers right around 20. A number of people listed on IMDb may fall off once their actual job description is clarified.
http://axamonitor.com/doku.php?id=does
In the article, I also have a quote from Star Trek author Dave Galanter, who asked his name be taken off IMDb after Alec Peters overstated his participation in writing the script for Axanar:
I didn't get to edit any story and neither asked for nor wanted any credit for giving [Alec Peters] comments and notes on his first draft. … Peters was trying to “thank me” for giving him some comments early on, but had this been a professional endeavor of mine, the script would have had to have been licensed and approved by CBS or Paramount, and I'd have needed to be paid. The input I gave was the same I give to beginning writers at writing workshops I take part in for free.