i can't really find an official definition for what a family game is or not, but i mean, it's essentially the same as a 'family film' in regards to the use of language. so, while 'family game' doesn't have an objective definition (yet), 'family film' does. it's "a film genre that is designed to appeal to a variety of age groups and, thus, families." i think we all agree that the game appeals to many age groups. i suppose we could also agree that the game is PG-13 considering that a player must be 13 years or older to play (with parental consent). films typically are upgraded to PG-13 from PG when language is used sparingly (generally, less than 4 times) or the movie is especially violent. note that Glitch never uses language and is never violent, so the game really should be PG or even G. Certainly, it would be rated E for everyone with a disclaimer that they cannot control the content experienced online.
ultimately though, the game has parallels with a family film that's rated PG-13. and as such, we shouldn't use language.
thank you for your time.
(edit: ToS says 14 years or older, so I guess PG-14 would be more accurate.)