aren't most languages invented and initially developed within a private company? Go, Dart, Java, JavaScript, C#, F#, VBA, Kotlin, Erlang, C(at AT&T), Rust (at Mozilla). The list is probably very long
Most of those are open source, and while initially developed at a private company, most are run by non-profits (such as the Rust Foundation for Rust). Also, the language itself is not usually the main product at those companies.