Aren't these all standards and hence not directly comparable to software (so the label of "open source" can't really apply)?

In addition, aren't they all open and royalty-free — i.e. the closest equivalent to open source?

In contrast, OpenAI does directly produce software.

There are arguments to be made that AI shouldn't be open, but the name of the company is misleading.

You can take the OpenGL spec. and write an application or your own implementation based on it, nobody is going to stop you, check your project for prohibited language or terminate your OpenGL license for inappropriate use.