The fact that it’s in English doesn’t preclude its use by the non-English. For example, I (a Dutch person) just found out about some Brazilian and Panamanian s

The fact that it’s in English doesn’t preclude its use by the non-English. For example, I (a Dutch person) just found out about some Brazilian and Panamanian slang. Presumably, a Brazilian or Panamanian person could also find out about Dutch expressions (I saw some Dutch entries). So the target audience, to me, is quite clear: people from around the world, who are interested in other languages and cultures.