Or let me put it differently - what's the most popular open source client?
Or let me put it differently - what's the most popular open source client?
It's just the basics - only renders terrain and some static blocks. But it's also based on 1.7.3 protocol.
I've just checked and it kinda works with TrueCraft server: http://i.imgur.com/Brf2NXg.png
Another open source Minecraft-compatible client in the works is https://github.com/thinkofdeath/steven. Written in Go, already decently functional, though still far from finished it is under active development and progressing nicely. Not that popular yet but seems to be promising to me. The author is a major contributor to one of the most popular Minecraft server software packages.
TrueCraft is a Minecraft implementation.