Maybe. But "Free Sign Up" sounds/works just fine. Having said that, a hint of a potential "but" (i.e. trial-ware) is good at times so that the users don't take

Maybe. But "Free Sign Up" sounds/works just fine. Having said that, a hint of a potential "but" (i.e. trial-ware) is good at times so that the users don't take the free part for granted and they are aware of an upgrade option.