I was going to ask how your implementation compares to Versor[0] but I see you link from it in your readme. My next question was going to be if there are any license issues, since Versor was for a long time only free for non-commercial use, but I see their github is a bit more recently updated than their home page and mentions it's now under the BSD (yay!). Lastly, are you concerned about the patent on the conformal method? [1]
There are a lot of great resources linked in this thread. My memory of the last time I took a dive into GA was that there was a split in the resources for representation -- one side tried to do everything axiomatically and symbolically, the other side had some concrete numbers but it was mysterious how they all worked together. Have you seen a super-basic resource that goes through the same sorts of modeling problems middle school and high school students do when first learning trig and classic geometry?