Sylantro Systems has just released a new software that will let telecom providers deliver voice over Internet Protocol services to subscribers of Yahoo’s instant-messaging service.

Free calling exists already among users of Yahoo IM, which allows any two “chatters” to plug headphones into their computers and talk at no cost. However, although Sylantro still has no formal involvement with the Internet company, Yahoo has yet to see significant traffic among plans that charge subscribers on a per-minute basis.

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