Thunderbird has been maintained with security fixes since then. And the underlying engine, Gecko, stays pace with Firefox ESR, so that it can stay up to date with security fixes as well. Firefox ESR just moved to 38.0 so Thunderbird does now as well.

There are no new major features or anything coming to Thunderbird, just bug fixes and security updates. So, it's still the best email client.

That is what was once announced, but (a couple years) after that Mozilla announcement, control was indeed transferred to a new group of people who now govern the project and do indeed work on new features as well.

There are more details on the website, e.g.: https://blog.mozilla.org/thunderbird/2014/11/thunderbird-reo...

There's still community involvement.

That's referring to contributions by paid staff. It's still an ongoing open-source project that may be contributed to by the community.

There are volunteers and paid developers from other companies (Fastmail, Softmaker) working on or contributing to various parts of Thunderbird.

that's kind of funny: fastmail's good web interface and caldav support is the reason i stopped using thunderbird.