Rust is one that's developed in the open. Commits to Rust's master branch must be done through pull requests on Github. All PRs must be approved and reviewed before being merged, and the approver cannot be the same person who submitted the PR. Furthermore, major changes to the language must undergo an RFC process, which is also coordinated via a Github repo: https://github.com/rust-lang/rfcs/ .

>Commits to Rust's master branch must be done through pull requests on Github. All PRs must be approved and reviewed before being merged, and the approver cannot be the same person who submitted the PR.

Any company that puts half an effort into open washing will follow these same procedures, so they aren't safe indicators that the real decisions aren't made behind closed doors ahead of time.

Paying close attention to things like the rfc process and approval process for commit rights and whatnot usually tell the real story.

Scala (https://github.com/scala/scala) is completely developed on GitHub with Pull Requests requiring reviews being the only way commits can enter master. Issues are in a separate JIRA instance, although there is currently some experiments about migrating that to GitHub as well. A lot of other processes about the language, such as discussions about language features and their design, also are open on GitHub.

Its little brother Scala.js is entirely developed on GitHub too, complete with language proposals and issue tracking. https://github.com/scala-js/scala-js

I've had a couple submitted pull requests merged into Elixir. The review process was very quick and painless.

Yes, I can confirm this. Development on Elixir (https://github.com/elixir-lang/elixir) is done in the open and on GitHub.

D is developed on GitHub and is open. Albeit there is no enterprise funding the development, it's small community is pushing the language forward. PR are reviewed and merged. But honestly sad to see it at the bottom of the list.

Erlang (https://github.com/erlang/otp) accepts PRs on GitHub, although they maintain their own JIRA instance for issue tracking.

Development of Nim (https://GitHub.com/nim-lang/Nim) and its tools is done openly on GitHub.

The three Microsoft ones (C#, VB.NET, TypeScript – PowerShell is curiously missing from the list, though) are openly developed as well. I'm not sure there are many popular open-source languages these days where the developers work behind closed doors and only throw code dumps out every now and then.

It's not on this list, but Eve is being developed in this manner: https://github.com/witheve/eve

Everything we do is through GitHub issues and PRs.

Haxe is developed totally in the open.

D is open.

OCaml now uses Github as its official repo and accepts PRs.

PHP is definitely an open process.

clojure is close, but not done on Github. All work must be through jira/bitbucket but anyone can sign up for free with the only requirement is of a CA.

Red - Everything is open and on Github.

PureScript is open as well.

Pony is developed entirely on Github, using the issue tracker and pull requests: https://github.com/ponylang/ponyc