Music License

Hi,
i am kinda confused and i don't have a lot of experience with the whole CC license stuff.

When an album says following:
"You can copy, distribute, advertise and play this album as long as you:
- Give credit to the artist"

http://creativecommons.org/licenses/by/3.0/

Does that mean i can even use it for commercial use?

I realize you can license the songs with jamendo pro but does that just mean you buy the rights of the songs so they "belong" to you, or do you have to do it when you want to use them in commercial projects as well (even when you give credits)?

as far as i know credits are enough as long as you do not sell the song as it is, under this license. (You cannot get revenue just by selling the song itself but you can use it on commercial projects?)

Tried asking the composer?

Thanks,
i guess asking him would be the easiest way, dunno why i haven't thought about it lol.