A lot of users are asking me that, so I'm gonna write a quick answer here on the forum:

in version 1.0.0, you can allow registered users to download/listen songs, or you can totally disable this feature, but you can't choose to let everybody to do this. In the forthcoming version I'll add a parameter to allow that, but meanwhile, if you're running 1.0.0, that's how you can solve this. You have to change a little bit (just a little bit) of the PHP code in 4 files:
[ul]
[li] components/com_muscol/views/album/tmpl/default.php -> lines 88 & 102 -> you'll see how the script checks if this is a registered user ($user->id &&). just delete this sentence. (this is the album view)[/li]
[li] components/com_muscol/views/song/tmpl/default.php -> search the same condition and delete it (this is the song view)[/li]
[li] components/com_muscol/views/songs/tmpl/default.php -> do the same (this is the songs view)[/li]
[li] components/com_muscol/views/search/tmpl/songs.php -> do the same. this is the search-songs view[/li][/ul]

IMPORTANT: Please, make this changes only if you're familiar to PHP and you know what you're doing!