It seems that its being managed by a subsidiary of Mozilla, MZLA Technologies Corporation: https://www.zdnet.com/article/mozilla-moves-to-monetize-thun....
Apparently they are hiring: https://www.thunderbird.net/en-US/careers/#apply
Apparently they are hiring: https://www.thunderbird.net/en-US/careers/#apply
I am skeptical about using a "monetized" mail client.
Do you have a TL;DL?
One thing I do remember is Ryan explaining how just being willing to directly ask people for money has been surprisingly effective.
It's also worth putting Thunderbird's relationship to Mozilla in proper perspective: for all intents and purposes, Thunderbird is a completely independent project. Since 2017 (https://blog.thunderbird.net/2017/05/thunderbirds-future-hom...), the Mozilla Foundation has primarily acted as Thunderbird's fiscal home, providing support for donations / bookkeeping / taxes / legal matters much in the same way that the Software Freedom Conservancy hosts Git, Homebrew, Inkscape and others, or how Software in the Public Interest hosts PostgreSQL, systemd, Xorg, FFmpeg, 0 A.D, and more.
If I understand last year's MZLA Technologies announcement correctly (https://blog.thunderbird.net/2020/01/thunderbirds-new-home/), it sounds similar to the split between the Mozilla Foundation and the Mozilla Corporation, where the former is a legal non-profit and the latter entity is for-profit and able to enter into commercial, revenue-generating agreements, but still wholly owned by the non-profit Foundation.
...But you should really listen to the podcast, I could be getting all of this wildly wrong.
> Why we need donations
Thunderbird is no longer funded by Mozilla. Fortunately there is an active community keeping it running and developing it further. But to survive long term, the project needs funding.
Thunderbird’s funding goes toward the significant infrastructure and staff that must be maintained to deliver the application to our tens of millions of users. For Thunderbird to survive and continue to evolve, we need your support and ask for your donation today. All the money donated will go directly to funding Thunderbird development and infrastructure.
They aren't receiving any funding so there is no expectation of profit. I assume the project will be around so long as enough donations keep coming in to make upkeep worthwhile.