Chronotron allows you to download YouTube clips and also to stream videos without downloading them.
In Release 151 and older versions of the app, though, the Search functionality in the YouTube flyout may no longer work as expected. Release 152 and later should be more stable when it comes to searching clips.
Still, if you encounter issues while searching, please be aware that you can use the Open URL dialog (Ctrl + U), to enter a YouTube URL to play.
And you can also download the clip from the same dialog! Downloading a clip works just like before, with the – hopefully minor – inconvenience that the actual search has to be done outside the app (i.e. from your web browser).
Chronotron 