OPC UAは.NETなしで？

 OPC Programmers’ Connection – OLE for Process Control

OPC-UA on Windows without .NET?

According to Microsoft’s PDC2008 overview, a session is promised on Windows 7 – Web Services in Native Code: "Windows 7 introduces a new networking API with support for building SOAP based web services in native code". This raises the enticing prospect of the full UA stack on Windows, without the cumbersome baggage of the .NET framework. We look forward to finding out more!

そうはなんねーと思う。

OPC UAの仕様を満たすにはWS-*の各仕様の実装が必要で、それ考えればWCF以外の選択肢は仮にWin7がそうなってもないと思う。