My understanding is that the distinction between manga and doujin is in their publication type and creation process: mangas are commercial books (so there are a least editors involved) whereas doujins are self-publishing works by the artist(s).
The book release list, on the other side, is the list of mangas released by FAKKU. Doujins
translated by FAKKU are also unlisted in that thread.
However, I'm confused to find that
Girls in Bloom by Maruta is placed under the Doujin category. I thought is a commercial book.