> Even if you are fluent in rust, it is going to require significant efforts to contribute to a new 1M LoC codebase.
Of course, but this is true for any project or any language, can hardly be disrespectful of me to chose Clojure just because you don't happen to know it? That sounds crazy to me.
> Contributors are the most valuable assets of an open source project
You're talking about something else. Open source is literally about "This code has a specific license that allows you to do X" where X and Y differs by the license. Contributors or not matters squat if some open source project is valuable or not.
Don't mix concerns here, you're talking about "open development" or something else, not specifically open source.
Sure it's hard to create a community and get contributors and what not. But a maintainer choosing a different language and people feel that being "disrespectful" instead of just "stupid" or "dumb"? No, give me a break, you run your projects your way, and let others run theirs that way, they're not made for you, they just happen to be available to you because someone was nice enough to make it so. Don't spoil that by acting so entitled about how they should maintain and develop their project.