Multilingual READMEs Are Helpful?

If you speak another language and can write it more intelligibly than google translate can, then yes. But just google translating your readme is not helpful. Anyone can do that themselves.

> Is it really helpful?

Have you ever seen a library/program that was written by a Chinese developer, but which had an English readme in addition to the Chinese one? Well, imagine if it only had Chinese.

I disagree with the other comment saying there needs to be an established community in the other language first. There are projects I would never have used or even discovered if they had been written solely in the dev's native tongue. But again, this is assuming you actually speak another language and can write it properly; a shitty AI translation will do more harm than good.

> How do you maintain single-source-of-truth?

The English readme is the source of truth. When you change that, change the TL too. If that's too much work, then just don't bother. An out of date translation is often worse than no translation.

If your project is multilingual, sure. Otherwise anyone can translate it on their own anyway.

Look into translation management systems for maintaining a source of truth. There's a lot of them out there.