I am new to the community so sorry that I don't know too much about what the proposed logos.
I still have to read up a bit on what is/was going on.
One thing that could be a reason, why no logo ever made it, is:
It's always hard to change a logo completely – not only Open Source but in the commercial world too.
Why? Because some people like the existing one and the quality of logo is often subjective so it can be impossible to argue well to completely replace one "that works".
And what is often forgotten is, that even a bad logo is part of a brand that people recognize. Even if the FreeCAD logo isn't perfect, it would be a shame to throw it out completely, because probably thousands of people out there recognize it
That's also why big company rarely change a lot at once, but incrementally instead (e.g. Fisher Price
It's also hard to say exactly how much a logo (or pretty icons, slick interface, fancy transitions) "is worth" in term of its impact on the user.
For those who are curious: A few years (?) ago I tried to visualize some of my thoughts on that topic similar which resulted in something similar to the food pyramid:
The further to the top something is, the more superficial it is (unless you have a lot of competition) if you view it just from the point of people using it.
More on that: stephanbogner.de/notes/pyramid-of-needs/
That being said maybe it would make sense to do an iteration on the logo instead of a fully new one. It would still be recognizable and the folks who like the current one are also happy
I messed around for like 10 minutes:
(This is just to get my point across, it's not a final thing)
I don't think it's necessary to update the logo of FreeCAD because the value is so great that it doesn't matter what the logo is (like vocx said on a previous page) but I'd be happy to help out if there is interest from the community – after all logo design is fun