I'm also curious about the claim too, as I can poke quite a few holes in it. Changing an MMO server to run on Windows after it ran on Linux isn't trivial, and also there is nothing that Windows Server 2003 R2 Enterprise offers that an MMO game server would need over just Windows Server 2003 R2 Standard Edition.

So, just read the linked PDF, NCSoft never migrated from Linux to Windows. They ran Lineage 1 on Windows NT 4, and ran Lineage II on Windows 2000. The upgrade to 2003 occurred to also move to 64 bit.

I'd be more impressed by a story of an actual major Linux using service moving to Windows in an ad like this, over "Company running Windows continues to run Windows."