Eaglercraft

Eaglercraft is a free, open-source, browser-based clone of Minecraft that can be downloaded as a single HTML file. It was developed by lax1dude, who continues to add new features to the 1.8.8 version of the game. 

Eaglercraft can be a challenge for IT directors because the file can be downloaded locally and doesn't hit the server. Some websites that host Eaglercraft may make money from ads.