(UPDATE: Newer versions of PPC Media Center look somewhat different than the screenshot below and have additional features. The download link at the bottom has been updated to the latest version.)
I ought to complain more often. Just a few weeks ago I wrote a post about Vevo branded videos on Youtube breaking third party downloaders. Youtube-dl was the only one that worked, and it being command line, was slightly inconvenient. Well, lo and behold, good fortune knocked on my door (sent me email) and Adam A. left me a cool new Applescript app called PPC Media Center (download link at bottom). It's a simple and elegant GUI frontend for youtube-dl, and I can report on good authority that it's awesome.
Basically it works by copying a video link to the clipboard, launching the app, and pasting the URL in the text field. You can also assign a hotkey (with a tool like Spark) and use it to launch PPCMC QuickLaunch.app which makes the URL pasting automatic. More on that in the documentation. Either way, you'll see three buttons, all of which are fairly descriptive. From my testing on Youtube, the download and streaming buttons will give you choices of quality and then you're on your way. Streaming opens in Quicktime (Perian plug-in recommended), and the download button opens a Terminal window to show your progress. The "Check for Updates" button did just that and asked my administrative password to update youtube-dl in my /usr/local/bin.
All that and a cool icon.
Another cool thing, this being Applescript, is you can edit the script inside the app package with Script Editor.app. There's a little about adding site quality profiles in the documentation, and I wonder if it's super complicated to change the player from Quicktime to VLC or Mplayer. As the documentation notes, if you do make changes use the "Save" and not "Save As" command to avoid damaging the app bundle, and keep a backup copy of the original.
Download PPC Media Center here:
(1/20/2020: Final update - universal binary. Consult the Read Me for all the updated features.)
One more note, you may notice on the right I've added a new link to my blogroll. It's Mac OS 9 Lives, and it has a special focus on audio workstations and music producing which was always a strength of the classic Mac OS and still is. They also have an active forum section, so go check them out!