Great question.
The Free fonts within Kernest can be used at no charge.
All Web Native fonts fonts are free. In addition they have the characteristics I identified in Web Fonts – Identifying a New Species that make them better for web use than fonts without the Web Native designation.
These characteristics are; a large x-height, low stroke contrast, and open counters.
Feel free to add the ‘web native’ tag as you see fit within Kernest – and if you see a font with the Web Native designation that you don’t feel deserves the designation, let me know.
Thanks.