I have a free chatsite, and people ask me if there is a charge. Should I use muryou or tada? I want to indicate that my site is free. I see the term muryou written on free weekly magazines. Is the term used determined by what type of item/service is being offered for free?
Muryou is more formal and literally means free in the sense of "no charges apply". In your case case muryou is better, as it is less ambiguous. "Tada" also carries the meaning of "only" / "just" and esp if you say "tada no chattosaito" one would more likely interpret it as "this is just a chat site [in the sense if the above sentence continued as "...., not a scientific magazine"]