Webphone development with SL in C++

Question

When I started my own business webphone application in C++ I decided to use SL instead of Adobe Flash. To display video and audio I have used Ozeki voip sip sdk and the sample program for implementing web to web video calls from http://www.voip-sip-sdk.com/p_85-web-to-web-video-calls-silverlight-voip.html for testing. The video and audio quality is splendid, my only problem is its costly license. Have you experienced the same with it?  Any pros and cons? Thanks for your reply.