So, let's look at this group of people knowledgeable in programming et al, but not english. Sure, this group exists. It's relatively tiny though. English is the language in any (modern, IOW except where it didn't replace latin yet) science, including CS. The vast majority of other on-topic literature is english. It's hard to learn a decent amount of stuff concerning programming without knowing english.

You can't randomly mix languages in source code, and any other choice of common language than english would exclude a LOT more people from the project.

All of this isn't related to i18n/l10n of your application at all. People not knowing english is a much more relevant factor when talking about user interfaces. I actually plan to localize my Xmoji tool eventually, it's just postponed until more important stuff is done (I mean, I assume most people would get together enough english to be able to use an emoji keyboard after all, but of course, especially seaching would benefit from l10n).