You can use your Mac to record from the Motorola DCT-6412 Personal Video Recorder. Most of the ports on the DCT-6412 are not active (Ethernet, USB, etc.), but the FireWire ports are still active on some cable systems (Shaw and Comcast, for example). Using that knowledge, here's how to record stuff from the box to your Mac. You'll need the following:

1. OS X10.4.9 (only version I tested; it may work on others)
2. FireWire SDK #23 from Apple's Developer website (free account required to download).
3. VLC (Video Lan player for Mac) or MPEG Streamclip

Read on for the step-by-steop directions...

Here's what I did to make this work:

1. Connect the DCT to your Mac with a FireWire cable.
2. Check System Profiler's FireWire section; the DCT should be listed as connected. If it is not listed, then your box probably has the FireWire ports disabled -- talk to your cable company.
3. Download and install FireWire SDK #23 and either VLC or / and MPEGStreamclip
4. Locate and start AVCBrowser from the SDK.
5. Click "Open device - control panel".
6. Select the Plugs tab.
7. Click "Open Device." The text should change to "Opened by this app = Yes".
8. There are two channel settings on the plugs screen, set them both to channel 63 and click both Connect buttons.
9. Start Virtual DVHS from the SDK and click the Connect button.
10. Click "Set recording path" to tell the program where to save files.

You can click the Record button now to record what the cable box is sending to the TV. I hope you have a lot of disk space -- a 30 minute show with a 4:3 aspect ratio requires 1gb of drive space. Click Stop when done recording. The file that DVHS saves will have a .m2t extension. You can watch this file with the VLC player. Use File » Open, as double-clicking the m2t file won't work. Alternatively, you could use MPEG Stream Clip to convert the mpeg2 stream to a different format like QuickTime, avi, etc.

Note: Some programs will not record properly as they are encrypted (pay per view), but the regular broadcast channels should be clear. Please respect copyrights and only record stuff for personal use.

[robg adds: I don't have this machine, so I can't test this one...]