There are a few free and commercial solutions:
- Virtual Audio Cable
- Jack Audio
This is free for the first 15 minutes, then costs $32 for the full version.
This is more geared for video recording, but could work if he wants to also use video.
Not a free option, and a limited trial version is available but it's a little complicated.
This is an open source, free solution that can be used with Audacity to record the audio.
Check out Ander's podcast: Maximum TORcast.