For the first, the README says it's logic.py and not nway_logic.py that has the article's code. (The latter is a generalization that was actually written first.) logic.py was extracted from the text, and the transcript tested against it.

I've just backported the renaming to Constant into nway_logic, and that example should work unaltered now -- thanks!

For the second, the interface to the decision diagrams does not use variables with names, as explained under 'Systematic succinctness' and demoed in make_alu_inputs() -- I aimed for the simplest code that shows the ideas. But I think you're right that bdd.Variable should've been called something different from logic.Variable.