It's just a number of independent computers that have been kind enough to install software, one of the features of which is running distributed computing jobs while cpu usage is detected to be idle and without an interactive window session.
What's a botnet? How would having one IP per worker (except in the case of NAT at the ISP or LAN/WAN boundary) defeat a purpose? Is a "botnet" a more efficient way to do what I'm doing? Is there either open source or reasonably priced software to manage the deployment of the original software and subsequent tasks (think hadoop but without hdfs, etc.)? I'd love to be able to do this with bitcoin to support the economy.