Spoiler: on buying and sharing doujinshi
showBecause I don't know Japanese, I actually didn't know that about doujinka not wanting people to resell their work. Its understandable of course, because doujinshi are drawn and published for a specific time period. They can't stand on their own like a manga or anime can, so the reselling part makes sense. At the same time, there are bookshops in Japan that sell doujinshi alongside the manga that it parodies, so perhaps newer circles don't think like that anymore. I think its a bit old-fashioned to not want foreigners to buy them. In Genshiken, there are two American women who come to Japan to attend Comiket, and they buy multiple copies of doujinshi just so they can take it back for their friends to read. Even though Genshiken was published in the mid 2000s, there wasn't any negativity towards those characters (in fact one of them is quite popular in fandom!).
How ethical is it to scan and scanlate doujinshi? Its as ethical as scanning and scanlating manga, to be frank. I actually started buying doujinshi earlier this year through proxies, and its definitely worth it, even when its expensive. Because the manga that I'm into aren't popular titles, owning and reading doujinshi assures me that its popular enough. Its kind of silly, but when a manga doesn't have much fanfiction or fandiscussion going for it, doujinshi fills the gap for me, even if I can't understand it. On tumblr there's a blog of a very dedicated Gintama fan, and she often posts pages from the scanlations, but sometimes she posts doujinshi scans too. Its weird to see the two side by side, one post after the other, but to the blogger the doujinshi was validating things she liked about Gintama. So because I understand that, I don't think scanlating doujinshi is that bad. Its when people start taking it for granted that you question how much knowledge has been lost in the process of its translation.