An internal Google memo was released of an engineer reviewing possibilities and ranking Java as the only viable one.
I did find a WSJ article with a quote from a Google engineer:
"We have been over a bunch of these [alternatives to Java] and think they all suck," the Google email continued, according to the transcript, adding, "We conclude that we need to negotiate a license for Java." [0]
[0]http://www.wsj.com/articles/SB100014240531119035202045764826...