Yes I'm being a tight wad, but as a Linux user I am used to getting a lot for free and I don't have a credit card and I prefer OSS in any case. Nor do I want trashy ( YOU ARE THE LUCKY 999,999th VISITOR CLICK HERE TO COLLECT YOUR PRIZE) style adds anywhere on my website insulting the intelligence of my customers.

I believe people avoid using things that spawn new windows, bother them for registration or interrupt them from what they were trying to do. Hopefully that was browsing for books they intend to buy from me. So I wouldn't want applets popping up (covering my website) and asking them to login, download software, or otherwise distracting them. I want nothing more than a button on my website which activates their microphone or perhaps plays an alert sound on my machine. I could then activate the chat which should remain seamless and invisible while they are on my site until they or I toggle the button to end the voice chat.

This speaks for itself really. The less any embedded application expects from the client machine the better. I won't use a windows only solution for either the client or server side and It should be browser independent also.