Is itunes the only place that you can download songs for your ipod?

No, there are plenty of other legal ways to get music on your iPod, including google Play, AmazonMP3, as well as streaming apps like Pandora and Spotify. What determines whether or not it is legal is if the record companies and artists are being paid their fair share. So if you are getting songs and albums for free download from a website that doesn't sound familiar, or getting them from file sharing websites like Limewire, then it is probably illegal.