Yeah there have been a bunch of UE3 MMOs (usually they write their own server stuff, I bet) but I dunno if any have been UDK explicitly. Either way, this HTML5 Runescape stuff is almost certainly not any form of Unreal.
UDK != UE3 || UDK != UEX (here X is any version of Unreal Engine) http://forums.epicgames.com/threads/806286-MMORPG-with-UDK-Android http://forums.epicgames.com/threads/755565-Is-it-possible-to-create-an-MMO-with-UDK/page3?highlight=MMORPG You need full source code. I have done my research, go search on Epic Game's forums…