Doppio's lineage goes back even further than 2012. A "JVM in JS" was given in Emery Berger's 691ST course in the fall of 2011. My notes show that I submitted my "finished" JVM on October 26, 2011. I say "finished" because it became obvious rather quickly that a lot of things would be difficult if not impossible in JS (like threading and synchronization) and so we negotiated with Emery to come up with a subset of Java that we could reasonably implement for a class project. IIRC, there were 6-8 VMs written that semester.
Doppio proper (the repository you refer to) started during the spring meeting of 691. Those guys went above and beyond the minimal spec we implemented, and they tackled a lot of stuff that we thought was impossible. Thus the research paper.
IIRC, we also had to write a decentralized chat program in JS that semester. That was also "fun".
One year before asm.js appeared, in Mar 2013
Three years before WebAssembly appeared, in June 2015
Five years later, In 2017, WebAssembly still doesn't have a GC and cannot run the Java/Scala/Groovy programs that Doppio was able to run in 2012