There's no custom framework invented here. Instead, the case study was designed to discover minimum viable patterns that are truly vanilla. The result is maintainable, albeit verbose and with considerable duplication (most of which may be mitigated by ES6).
If anything, the case study validates the value of build steps and frameworks, but also demonstrates that standard web technologies can be used effectively and there are only a few critical areas where a vanilla approach is
clearly inferior (especially in browser testing).
I'd love to hear feedback on the app and the study; let me know what you think :) The full source code and case study can be found here: https://github.com/morris/vanilla-todo