Install license free fonts in Ubuntu

Free font Open Sans

First find a good font licensed under a free license, such as the Apache License or the SIL OpenFont License:

This example from uses Open Sans Font Family:

Create a folder for it, enter the folder, download the font, and unzip it:

mkdir -p ~/.fonts/truetype/open-sans
cd ~/.fonts/truetype/open-sans

If the program you want to use it in is open (such as Gimp or Inkscape) you need to restart it, to enable the font.