I know from personal experience that OBS (Open Broadcaster Software) works with capturing only the cataclysm window at least with the SDL version it worked a few Versions ago (I think I tested it with version 0.7?). In the most recent version of OBS I know you can save to file instead of streaming too.
OBS produces compressed video files though and not .avi so depending on what you want to do with the video you might wanna look into other software, I like it because it doesn’t fill up my hard-drive, but if you want to edit your footage your editing software will probably mangle the quality when it re-encodes the video.
EDIT: Definitely still works, on a side note OBS is fairly resource intensive and will hog your CPU on high resolutions and good quality.