From Web Education Community Group
Over time it was clear though that Microsoft had no intention of cooperating or implementing proper JS in IE, even though they had no competing proposal and they had a partial (and diverged at this point) implementation on the .NET server side. So by 2003 the JS2/original-ES4 work was mothballed.
Alas, there was still turmoil between the various players; Doug Crockford — then at Yahoo! — joined forces with Microsoft in 2007 to oppose ECMAScript 4, which led to the ECMAScript 3.1 effort.
In July of 2008 the disparate parties on either side came together in Oslo. This led to the eventual agreement in early 2009 to rename ECMAScript 3.1 to ECMAScript 5 and drive the language forward using an agenda that is known as Harmony.