[Sergej] Müller is discontinuing his WordPress contributions due to health reasons, but he plans to find a suitable successor who will be able to deliver the level of quality and support that his users have come to expect. His plugins, most notably Antispam Bee, Cachify, Statify, wpSEO and Optimus, are used widely around the world, particularly throughout Germany, Austria, and the germanophone parts of Switzerland.
Antispam Bee is a great alternative to Akismet and I hope his plugins are picked up by responsible folks that can carry on his legacy. I hate to see someone having to leave a passion project, but especially when the reason is health related.
Sarah Gooding did a nice job in the WP Tavern post describing his influence on the German WordPress community, and it appears by all accounts that Sergej's efforts and general community involvement will be severely missed. Apparently, he is “currently in conversations with parties who are interested in his projects,” so we should find out more about the fate of his plugins soon.