Why is it different than the other cards?
CableCard is intentionally designed to be a huge, expensive pain in the butt to implement on commodity PC hardware. Until about a year and a half ago (or maybe a bit longer), it was
impossible to do in any application other than Windows Media Center.
They've relaxed the restrictions somewhat, but you are essentially still supposed to pay a huge amount of money to CableLabs for a license (and for compliance testing to ensure you implemented all of the required DRM schemes).
Open Source alternatives usually either:
1. Only implement unencrypted CableCard content (Copy Freely tagged). For Time Warner cable in my area, this means ZERO channels work.
2. Hack around it and ship things in clear violation of the licenses, which opens them to lawsuits. For open source projects, often no one cares (because there is no corporate entity to sue). But, JRiver can't do that with a commercial product.