I thought Mozilla still owned and thus funded Thunderbird.
Someone must be ensuring that employees who work for the Thunderbird project are being payed even if it is a mostly community ran project.
The donation page still takes me to a Mozilla branded donation page which makes me think they are putting some resources into the project even if it isn't as fully funded as most would like.
The donations they receive via that page go directly to Thunderbird is my understanding. There was some chatter a few years back where I guess Thunderbird had some restructuring done so they could have better funding, I forget the specifics I remember discussing it here on HN though.
The donation page still takes me to a Mozilla branded donation page which makes me think they are putting some resources into the project even if it isn't as fully funded as most would like.