Normally, you should address Yahoo! Japan topics 
on that particular forum, but I went ahead and 
asked a friend in Japan about the auction.  This 
is how he translated it:

"Hisashiburi!  I had a quick look at your auction.
This is a fan-made (dou-jin) cel the seller made
personally, apparently borrowing the image from
a Megami-sama movie calendar.  It's hand traced
and hand painted using professionaly tools to be
as close to the real thing as possible, and the 
seller guarantees no notable flaws or mistakes."