Don't you love it when someone who is caught using another's lineart without crediting them gets all huffy and righteous? The work is not yours no matter what "changes" have been made to the piece. Please have the good manners to either use the Artcircle's name, or if you came across the lineart in a gallery and don't know the artists's name, a note of that therein.
For those who don't know, doujinshi is a form of fan-manga in Japan. These books run the gamet from simple stories printed on a copier to eleaborate books that have parcment covers and elegant front and end papers. Some well known manga artists have gotten their start in this fan