The Truth About IceFrog

This is a very important news to us, do we really know who Icefrog really is? There are rumors circling around the net talking about The Truth About IceFrog wherein an employee at Valve working on an unrelated project from IceFrog said that Icefrog already worked for Riot Games and S2 Games but didn't told Valve bout it.

What can you say? Is it true or not?