A Guest Post by Shannon Byrne in Free Offers Ever wonder why every major restaurant chain has invented its own birthday song when “Happy Birthday to You” is literally the most recognizable song in the world? It’s not just because it’s hard for servers and patrons to clap along to – it’s because the proprietors want to avoid copyright infringement. That’s right: the 150 year old tune is still under copyright until at least 2030. (That’s also why you’ll seldom hear it in movies or TV shows, either.) Even though you have to wait ‘til…