http://www.sound-effects-library.com/terms.asp

t&c's from an online sfx library i used to work for.

"7. For the purposes of creating so called "library music" clips or so called "production music" clips intended for commercial exploitation, the included audio samples may only be used "in combination" with other sounds within musical compositions. For example, any rhythm loop samples (which Sound Effects Library Limited or its Library partners regards as being musical clips in themselves) must also be combined with other types of samples or sounds to effectively form a new composition, rather than simply being looped. If in doubt over this or any kind of usage, please contact. "