You leave something alone for two months or more, most people assume it's dropped unless there's a notice about it somewhere. True though that they should've asked, but again, its been 3 months since the last update, that's DbA
I'm partially with Mfrost here; ghosting for 3 months without notice is good enough reason to assume you're no longer going to do it. They've only started explicitly because they thought you wouldn't anymore, expecting them to ask you for permission is a bit entitled; the manga doesn't belong to you.
When you don’t post a chapter for three months and only post one when undercut by another group... then proceed to whine about sniping and quality in the post page? Dude they wouldn’t even have scanlated the chapter at all if you didn’t take so long. You don’t own the manga.
Sure, it would have been better if he ask you first, but it was pretty fair to assume that after 3 month without releasing or announcement, you just dropped the project...