Does it mean you can download it to try out but if you want to use it you have to pay a license?

Demo means incomplete character set and/or deformations added to the/some glyphs as, for example, the word demo included in the glyph.

Usualy, a demo version is not fully usable.

And it mean too that "you can download it to try out but if you want to use it you have to pay a license".

I also would like to know for sure. Is it free or is is not?

It is *not* a free font. It is a trial font, a demonstration font. You download the font, install it and use it to see if it is the font that fits your needs. If it happens that is not the font that you wanted, you are expected to uninstall the font. However, if the font is perfect for your project, you should acquire a license to use the font. The font you downloaded should have instructions on how to acquire a license to use the font.