Hey DC, I found this thread very late so I guess you may not see this. I played with voxel.js for a while back in the day, but ultimately I wound up building a similar engine from scratch (I think we discussed it briefly, if this rings a bell).
Anyway, I thought you might be interested to know that Minecraft Classic seems to be built on my voxel engine, the one I modeled after voxel.js! So there's a kind of circular lineage now, from minecraft to voxel.js and later back to MC...
I worked on it for years and I had high hopes, wrote about my progress here: https://medium.com/@deathcap1/six-months-of-voxel-js-494be64.... Inventory, crafting, chests, texture packs, a plugin system, and embedded web views were some of my favorite features. My project was https://github.com/deathcap/voxelmetaverse, hosted at http://voxelmetaverse.com.
Unfortunately I haven't had time to develop it further, but it is all open source if anyone would like to pick up the torch.