I would like to use Fontello for my templates that I sell. I didn't understand its license's documentation very well. Can I use it for commercial use or not?
Different fonts have different licenses, but it seems that Fontello only includes fonts that allow commercial use. (See section 2 below.)
All licenses are defined by original fonts authors. Fontello doesn't add any additional requirements. License type is shown on the right from font name.
Fontello includes only those fonts, that do NOT have limits for your websites (non-commercial use, mandatory links, mandatory attribution, and so on). Since we are open source developers, we don't wish to restrict your freedom.
You can just use fonts on your website and be happy, but it's considered a good practice to credit authors in unobtrusive way. There is no need to inform the entire world on your main page with big letters, that your site uses font XXX. Just if someone really interested to know - it's good when he can find such info.
For your convenience, we prepare a LICENSE file with attribution in each generated archive. It includes info about all fonts with selected glyphs.
Source: https://github.com/fontello/fontello/wiki/What-about-license%3F