I follow Godot since it got open sourced some years ago - great project.
What scripting language beside visual scripting does it support? Lua? Squirrel? or only C++? (I saw some screenshots there: https://godotengine.org/features )
Their stances haven't really changed, they introduced GDNative which is a system that loads shared libraries using a C API, which has made it easy to add and use any language (I'm guessing the original idea was to make using C++ in your game easier). Some guy made C# bindings with GDNative, so they're making it optional with the release. There's other languages you can use as well. GDScript is still the 'main' scripting language.
That's plain wrong. C# bindings have nothing to do with GDNative, it's a module on it's own, integrated pretty well and unlike things that can be bound through GDNative, Mono module will be a part of Godot itself.
My bad, there was a bit about C# in their article about GDScript on their website, read it wrong. You're right, took a peek at the code, it's a regular module.
What scripting language beside visual scripting does it support? Lua? Squirrel? or only C++? (I saw some screenshots there: https://godotengine.org/features )