This is a complete rework of how Kaleidoscope is built, but should be largely transparent to most developers and completely invisible to folks using the Arduino IDE.
Some advanced features of kaleidoscope-builder config files have gone away, but it’s likely that @algernon was the only person using them. The tradeoff is that we’re now using a much better maintained build tool under the hood and that we’re no longer as tied to a single specific directory structure.