Who should approve local phrasing when the founder does not speak the language?

Separate factual product approval from language review. The founder or product owner checks what the demo claims; a capable reviewer checks whether the local wording carries that claim accurately. Keep both decisions attached to the same asset version.

Give the reviewer the target customer and the intended action, not just a sentence to translate. Ask them to flag ambiguity and cultural assumptions. A back-translation can help expose a mismatch, but it does not replace judgment about how the original line reads to a local viewer.