I would like to announce that Stamp collection module is now seeking a new lead maintainer.
This was my very first Moodle plugin written back in 2007 and it has had very special place in my developer's heart. That is also probably a reason why I hesitated for too long to offer it for adoption, even when I effectively stopped maintaining it around version 3.4 and haven't updated it since then.
Naturally, I would do things differently today - including the name of the module which was not well chosen. If I started with it today, I would probably call it "Stickers" or "Stickers collection". But actually - I think there are better and mainly up-to-date solutions covering the same educational scenario such as Badges or Level XP or similar gamification plugins.