It would be very cool to be able to add a sound to the project tree directly from the freesound database: http://www.freesound.org

Sure, that's a great idea. However, having checked their pages, there is currently no easy way to use their web site for an easy querying / downloading of audio samples.

I also saw that they are in the process of completely redesigning the website (see their blog: http://www.freesound.org/blog/ ) and choosing a different license for the uploaded samples, so we need to wait until the redesign is over to see what will be possible.

In all cases, I think we should ask them if it's ok if we implement an easy search & download feature in a video editor... Maybe if their new website offers a possibility to do it, we could also add an option for easy upload...

Uh, why not just open a browser window, find what you want, and download it? Why not add openclipart.org, archive.org, blip.tv, garageband.com, jamendo.com, and so on, and so on? Where does this end? OTOH, I like the existing, kdenlive-specific online features.