That's why most international institutions, wether private or not, define 'official languages'.
When it isn't, it often involves translators, in numbers ranging from a few to armies.
Most software out there being freely supported by at most one person, do you really think any of them have the resources, time, to find multiple translators willing to work for free on translating their project? Or, heck, pay them on their own dime for it?
No. So most developers know that if they do not work in a language that will be understood by most other developers, their work will essentially be useless to everyone, no matter how great it may be.
Honestly, we're lucky to even have a lingua franca. It could be Egyptian hieroglyphs, for all I care. It just happens to be English. And that is fine by me.
Indeed, and some of those multilingual people are developers bridging between the world of international software where English is the lingua franca and their own local communities where company-internal code doesn't need to have all documentation in English, even if that's the case for the open-source software it relies on.
The bridge also works in the opposite direction, such that if you want to contribute your internal code to the international community, it's appropriate to provide them with English documentation. The TARS developers evidently realize that, their translation is just not fully done yet.
You know, it doesn't change anything if while you steal something you are yelling "it's not theft". It works the same in other situations too, like when you argue all other cultures should speak the same language as you.
Language barriers are inconvenient, but they can be overcome in well known ways, so they are certainly not the cause of breakdowns in international cooperation as all that is mostly done by multilingual people anyway.