The development of BlockJS is currently paused in favor of Cavesiter—a mod that will serve as the "main game" of BlockJS. It will be publicly released around February. Cavesiter will support way more things than BlockJS like improved shaders, more textures, a modding API, SSO auth system, etc. It will be compatible with BlockJS from versions u6 and if you're not using the Cavesiter client, please install the Cavesiter Core mod (which is also in the works) to allow Cavesiter to be installed. The source code is currently in the works and expect BlockJS itself to get a better modding API.