I believe I can clear things up quite a bit. My technical experience goes back to the Bronze Age (the oldest disk drive I've ever maintained, repaired and brought back into service was a 50lb 3 foot diameter half inch thick oxide coated bronze/aluminum wagon wheel that looked exactly like a giant disk brake).
I also have grave concerns about personal and corporate security, but this isn't one of them.
Remember that everything that works "on the cloud" is based on the Client/Server model. That means that the Client (the user end) asks for information, and the Server (information provider end) provides it.
Of course, information does flow both ways, since the Client has to send information out to get the Server to respond, so it's always possible to pervert the provider/consumer relationship, but in the case of Abasoft we pretty well know what their motives are: they make money selling their Server to people who want to broadcast to the world. When you set up one or more Servers for this purpose, the only things you put on them is the Server and your Content. The Abacast Client is simply a protocol conversion filter that plugs into your browser and processes (decompresses and translates) the incoming downstream to your player. Abacast pays the expenses of developing this client (gives it to you free) because it enables the valuable Server transmitter they're selling.
I would add that the biggest threats to your security and privacy are the operating systems (Windows, Android, iOS but not Linux), and your browsers (Google, Bing, Yahoo but not Ixquick), because these not only track and record everything about you but make it all available, ostensibly to authorities (warrants no longer required) but also to anyone with intermediate computer skills and an inclination to dig. So if you're concerned at all about personal security, get yourself a Linux laptop, make Ixquick your default search, and keep your sensitive stuff strictly on an encrypted drive. For everything else, try to limit your exposure and just assume everything on your "public persona" is totally public, including where you've been with it, because basically, it is.