I have a requirement to download videos to play offline and came to know about your service. However I am little suspicious as to why you require the page source to be copied instead of the URL of the video page. I am afraid if any Personally Identifiable Information will be available in the page source that you might use.
Can you clarify the reason for asking for the page source instead of the URL?
The main reason is, if a user sends the URL to our web server, the server itself needs to download the web page of the URL from YouTube and parse the download information. At first we had actually implemented our YouTube downloader in this way. However, YouTube has a protection mechanism: when it finds out there are too many requests to visit YouTube website from a same address, it will ban that address so our server will be not able to download any video. This became a problem when our website started seeing 100+ visitors per day (now our tiny server serves 7000+ download requests per day thanks to all our great users like you!)
Regarding to your concern about the Personally Identifiable Information you mentioned in your feedback, there is a piece of information that can be used to identify a visitor though. It is the IP address of the client PC. It is unique across the Internet so it can be potentially used to identify a person. This is true for KIBase.com as well as to any other website, even when a user visits a website without posting anything, his or her IP Address will be available to the server. The Internet is not built to be truly anonymous, but I believe it is still safe to use as long as we are careful and take enough safety measures.