Hello Martin33 and welcome to the forums
This is a very obscure topic and something which requires quite a lot of specialist knowledge. I'm afraid to say that, although I may be wrong, I doubt you will find anyone here who has any experience with this SDK.
I've never heard of this SDK, but then again, I've never heard of any of the competitor's SDKs either. I would suggest that you download the SDK and try it out to see if it suits your needs: Ozeki C# VoIP SDK - Download Ozeki VoIP SIP SDK
I'm sorry that I couldn't be more helpful!