All of the decent video-chat software I've seen is fairly expensive. It's only worth adding video-chat if it's a pay membership site because the cost to set up and run video chat is significant. So, if the commercial apps are out of reach, then you may want to reconsider having video chat at all. It eats up HUGE amounts of bandwidth and you need decent camera and sound equipment, too. If the quality of the video or sound is bad, people won't bother with it.