It's interesting that Domino's is presenting the offer in Taiwan, where they also offer a Kimchi Seafood Pizza and Okonomyaki pizza rather than here in the States, where sausage and pepperoni are pizza staples. In fact, as far as big chain pizza goes, only Papa John's has ever offered a meatball pizza in the US.
The meatballs are Italian-style meatballs made with locally-raised pork, salt, sugar, and spices.
In addition to the pizza option, the meatballs are also available in a ciabatta sandwich as well as on spaghetti with meat sauce.