This is a somehow irritating move. I maintain several sites (and a tutorial) which make extended use of the Members extension and now I ask myself what I should do. Keep it and hope that things do not break when Bolt upgrades? Wait for a new project to replace it? Write a new member extension from scratch?
I wonder: Could someone who still has the source just set up a new repo on Github, upload it again and make it available to others (it's a very permissive MIT style license)?