I believe that logically speaking; it's irrelevant except for one simple question "where/how is the art/porn piece to be displayed/publicized at a particular point in time and space?"
If you take the op's ( grinsegold )'s original post here "http://forum.makehuman.org/viewtopic.php?f=16&t=11918#p29030" he has posted asking if an image of the statue of liberty having a 'specific' kind of sexual relations with the statue of justice is to be considered art or pornography.
It's actually both and neither -- I say that based on the delivery intentions of the art/porn piece at any specific point in time.
- If the art/porn piece is to be displayed/publicized in a place where visitors would appreciate the concepts being portrayed then it would be considered highly appropriate: ( in this particular case, the idea that justice is being 'dis'served by what some criminal-minded people feel is their 'freedom' to commit crimes and also get respected for their damned crimes ) but this would be most suited for a political and/or anti-crime message.
- If the art/porn piece is to be displayed/publicized in a place where visitors would immediately perceive the piece as "pornographic" then it would be considered highly "in"appropriate: ( in this particular case, creating an 3D representation of the image concept in a 3D computer program for general-public viewing where kids, teenagers, their family, their schools, etc where such imagery could cause confusion and/or misunderstanding which could lead to negative impacts to the viewer ) it is best _not_ to do this in a place where general audiences are welcome.
- If the art/porn piece is to be displayed/publicized in a place where the artist may wish to showcase their art/porn piece for their own fame then it could go either way depending on for instance if they are applying to a college or for a particular job or even to attempt to get an award somewhere for something. They could be viewed as having great artistic talent or as having a very good political-commentary capability or as having a great creative way of sexual-minded thinking ----OR---- they could be viewed in the exact-opposite perspective, again depending on 'where/how' they intend to deliver their art/porn piece.
The only ideal solution is to have two forums or two sub-forums and clearly mark them as "Appropriate for all Ages" and "Mature Audiences ONLY!"
Unfortunately criminals and trolls would just purposely muck it up by doing their usual criminal cyber attacks which in the u.s. and many other countries around the world is an imprison-able criminal offence. Therefore the only way to mitigate that would be to have someone 24/7/365 monitor postings/uploads and decide which of the two sub-forums the post/upload should be classified into and then just moved to the appropriate place -- this is in many cases too costly or simply unavailable.
just my 2 cents on the matter....
p.s.
i'm not accusing anybody of anything here but i have to say that even tough I like lots of different kinds of art; I don't approve of using art to de-rail, destroy, or de-fame the good intentions of people like the MakeHuman staff who have very generously given us a fantastic program to create whatever artwork is in our minds.
Many thanks to the MakeHuman staff and contributors for your fantastic work!!