Inter started out in late 2016 as an experiment to build a perfectly pixel-fitting font at a specific small size (11px.) The idea was that by crafting a font in a particular way, with a particular coordinate system (Units Per EM), and for a particular target rasterization size (11), it would be possible to get the best of both sharpness and readability.
Inter is a free and open source font family.
You are free to use this font in almost any way imaginable.
Refer to the SIL Open Font License 1.1 for exact details on what the conditions and restrictions are.