I'll help you.

Develop an application for support of financial and tax regulations for a certain country. You will have verbs and nouns which describe the situation clearly.

You develop an application from specifications written another language than English. They exist.

The biggest failure I keep seeing are futile attempts to translate concepts under these circumstances into English.

I agree in this case: when you want to invite collaboration on github, English (or Chinese?) would be better suited.

Even in financial / tax software it is possible to create an abstraction in which you can safely write English code and move all specific terms into some i18n module. Of course if you are not clever enough to do that it's not that bad to use /required/ language, but in this case we talk about strictly technical tool for database modeling, so no excuses - it definitely needs to be translated in order to be accessible for other GitHubbers.

So, which language should American programmers use in their code?

What nation do you belong to?

I'm from Romania. Coding in your native language is likely used as a safeguard....it means it will be very hard to outsource the product :) . Coding in your native language on a OSS project is even worse.

Ever heard of Domain Driven Design? Your customer's problem domain is best expressed in their native language.

But for Open Source projects coding in English is probably the best way to attract contributors.