Some basics on licensing can be found here:
http://www.karaokeantipiracyagency.com/info-law.html
Regardinging the copyrights:
http://www.copyright.gov/title17/
I've seen the following books recommended:
Confessions of a Record Producer by Moses Avalon
This Business of Music: The Definitive Guide to the Music Industry.
I hope you get this because even though the links point to government, anti-piracy web sites, and other non-competitors to the sponsors and karaoke scene they generally frown on posting web sites in the forums. I hope they remain but it's hit or miss usually.