I stumbled upon this open source video gallery while looking for php video upload script. But can't find one and found this. If you plan to start your own youtube, you may want to try this.
PHP Director does not allow user to upload video, but it lets user to paste the URL of video clips from youtube. After submit the video to PHP Director, the application will retrieve all the thumbnail available from youtube. And user can start to name it and give some description of the video.