Soundcloud is great due to the no size restrictions... so I can upload full resolution .WAV files!!!! without having to pay to have a full priveledge account like many other music sites...
You cannot (it will not let you) upload copyright material however by uploading... a good page to look at a quick reference to soundcloud and legal info:
http://help.soundcloud.com/customer/...cs/39593-legal
This being the crucial part of what your wanting to know:
"After uploading a track or set, you can select under which license you would like to release your piece of audio on SoundCloud. You can later change the license via the track settings (click the pen icon above the waveform) at any time."