So, I had a tiny bit of a back-and-forth with David. Figured I'd share here. I am cautiously optimistic that at some point in the future there may be some better hobbyist offerings, but I'd guess if there is any forward momentum at all, it will take a long time, and probably consist of a lot of ...

Finally got a response which surprised me as this was my third (?) email over the past year on the same subject:

Hello [gered];

Thank you for your interest in our 65xx technology.

Your feedback is valuable and WDC is looking at ways to improve our offerings and relationships with multiple ...

I suspect they are providing "just enough" to do simple things with the SXB boards. For commercial purposes, the ($40?) registration fee isn't unreasonable, and the libraries support double-precision floating point, etc. But most people won't need that.

I'm going to try to run the trial version ...