You don’t need the HD version of UFO capture for SD cameras. I’m using UFO Capture V2.24 under Windows 7/64-bit. The PC has three PCI Osprey 210 video capture cards and I run three instances of UFO capture for three cameras, 2 Watec 902H2s and 1 other B&W monitor camera. The PC is an old Dell Optiplex 780 with an Intel E8400 CPU running at 3GHz and 8 GB of memory. Each instance of UFO Capture uses around 150MB of memory so they are very lightweight. Each instance will use a different CPU core if it can and even with all three cards detecting the CPU load never goes above 30%
I certainly prefer having a PCI card for the video capture since I occasionally had dropped frames using a USB dongle. The Osprey 210 is a really nice card. They are a bit pricey but occasionally come up at a decent price on ebay. I’ve never had any problems since I started using it.
I don’t know the details of their licensing model but the problem is solved if you use a single PC.