Font Awesome is fully open source and is GPL compatible. You can use it for commercial projects, open source projects, or really just about whatever you want.

Booking.comTime for a change? We are hiring great developers to work with us in awesome Amsterdam.ads via Carbon
Attribution is no longer required as of Font Awesome 3.0 but is much appreciated: "Font Awesome by Dave Gandy - http://fontawesome.io".
Font License

Applies to all desktop and webfont files in the following directory: font-awesome/font/.
License: SIL OFL 1.1
URL: http://scripts.sil.org/OFL
Code License

Applies to all CSS and LESS files in the following directories: font-awesome/css/ and font-awesome/less/.
License: MIT License
URL: http://opensource.org/licenses/mit-license.html
Documentation License

Applies to all Font Awesome project files that are not a part of the Font or Code licenses.
License: CC BY 3.0
URL: http://creativecommons.org/licenses/by/3.0/
Brand Icons

All brand icons are trademarks of their respective owners.
The use of these trademarks does not indicate endorsement of the trademark holder by Font Awesome, nor vice versa.