Earlier quoted context omitted.
I _think_ it mostly was, with the exception of binary driver blobs. At least a few years ago it still had very active dev community at maemo.org, so it is not inconceivable for it to be revived. Alas, the neo900 project died.
No idea if neo900 officially died, but unofficially the timeline on the bottom and lack of news on the website [1] say as much. I believe right now you're best off with /e/ in combination with a Fairphone 3. [1] https://neo900.org
Apparently he has always been passionate about open source, and I've always been impressed by his output. I'd love to see /e/ get some mind share on a decent platform.