Whilst I cannot see anything from a brief search that specifically forbids you from downloading videos from their web site, neither do I see anything that says you can copy them.
I believe you will need to discuss this with them yourself, and see whether they offer these videos for download. I don't think they do.
I?m trying to download/rip/whatever-you-call-it a video off of the c-span library (or at least a portion of a video). What program can I use (free, preferably) to do this? The c-span player plays swf files, if that helps.