Find all 0-licensed Sounds in Freesound.org and similar websites

[h]

If I have understood right, we do not need to care about licenses in 0-licensed things (or less so): good for remixes, changes and etc. Investigate whether there are other such licenses. With attribution required, we need to have more attention to sources so start with 0 -- other places to get such sounds in the style of Freesound.org?