Unless there is a specific license attached to a module (e.g. CC-BY-NC-SA), you technically have to ask authors if it's okay to do this, even if the module doesn't specifically say so. This is the only legally safe way. In practice though, most artists will probably not mind as long as you're not making a profit from the project, but it would be legally grey area (and you can bet that most radios streaming modules fall into this category as well).
Other radio stations with modules:
SceneSat focusses more on the modern site of scene music, but also has some good modules.
CVGM focusses more on video game music, including tracked music.
