They are nice to write the documentation in poor English, they could launch the product only with Polish documentation and then you would never be able to use it before someones translates it.
This is true. It is also true that I am not able to use it at present because I don't understand the documentation.
A large part of modern programming is getting one's code to work with external libraries. For this to be a joy (and not a pain) the library's API should be simple and the documentation well-written.
I'm sure I could understand this library, if I put effort into it. However doing that has added problems -- I might subtly misunderstand it in ways that my code works most of the time but not always. And why should I bother? Python comes with multiple ways of storing data, such as sqlite, which I've used before and like.
This is not to knock the people behind CodernityDB which for all I know might be an excellent product. But at the moment it's not one I would consider using.
[1]: I guess it's possible that 'Chinese' might be close too, but I have no idea how the different dialects (Mandarin/Cantonese) would affect this.
Cantonese isn't written down, strictly speaking; when you write Chinese, there aren't dialectic differences.
Also: Don't blame people for english lang proficiency.