Tech question for the Interwebs

Dear tech-savvy friends,

Does anyone know of a completely free video converter that runs on Mac and turns out high-quality video without throwing a watermark up on the whole thing?  I'm trying to convert a HD .flv file that I got off YouTube into something that iMovie and/or iDVD will recognize, to make a DVD of it for my dad. 

So far, I have tried the following programs:

VLC - creates choppy visual, apparently regardless of the settings I choose.  (I've successfully grabbed the audio off as a good clean file though.)

ffmpegx - Doesn't seem to correctly install the required binaries.  Attempts to convert result in a 4KB empty file.

iSkysoft and Wondershare video converters (as far as I can tell, identical programs) - work beautifully, but slap a watermark over the video.

iSquint - fails to convert, I forget why

Alternately, if someone has professional software and is willing to convert it for me, I will cheerfully send or drop the file to you.  (Original size: 26.9 MB.)

Thanks!