Ask the courts
Don't need too...(the courts don't have a clue anyway...never do.)
The software is open source licensed under the GPL, and needs to be because it runs on the linux operation system and has some really highly-integrated drivers.
And the software is NOT patented...its the process by which the whole "time warping" thing is implemented using a combination of hardware and software algorithms that is patented...
Recent changes in the GPL (and crap like this trial) have forced Tivo to limit is open source avialability to the bare necessities, that being the direct modifications to the linux kernal and drivers...but back in the day, you could have downloaded the whole blinking source code and built your own Tivo if you wanted to...
...they didn't care until someone built a better one...but thats life...