That's how covers work. They can be a nice thing — essentially quoting an artist you like — or they can be bullshit, like this.
It's not illegal, but it's not ethical.
It's not illegal, but it's not ethical.
http://www.slate.com/blogs/browbeat/2013/01/18/jonathan_coul...
To broadcast it on TV with people singing it, that requires a sync license. That requires direct negotiation with all parties who hold any copyright.
In John Coulton's case, I'm not sure what he was required to do in order to license the lyrics for his original cover; i.e. whether he paid the calculated rate or negotiated something else. But it looks like Glee owes to two parties at best (if they actually lifted his audio like Timbaland this could get ugly)