Not really.
The software as a whole needs to be verified across a wide range of everchanging rules, some of which are going to be a judgement call even among experienced accountants.
Why would people be interested in working on this project? It certainly doesn't break any new ground. It's just a long and ongoing grind to implement tax code rules. If for some reason, I have a lifelong ambition to work on accounting software, I'm sure Intuit, SAP, and Oracle pay reasonably well.
Many popular open source projects began as an open source version of something. e.g. linux. The structure of the software, to facilitate contribution, could break new ground.
I think the most significant and difficult-to-solve barrier is making contributing accessible to non-devs.
Sure it would be great if that was Open Source, but it does its job this way as well?
Perfect for open source - if decomposable, so each issue can be dealt with in isolation (or many can). e.g. using a "plug-in" architecture of some kind.
And somehow recruit non-dev folk - if you go to the trouble to understand some specific tax point, you often would like to share it, and also record it in some "easy to use" form, for next time (and a starting point for amendments).
Maybe a "tax DSL", "business rules"? Or a user specs it, and a dev codes it?