Trunkmill is free for personal/non-commercial use, AND commercial use.
Trunkmill is licensed under a Creative Commons Attribution-No Derivative Works 3.0 License: http://creativecommons.org/licenses/by-nd/3.0/
This means, that you can share the font as you like, but not make a new version of the font (e.g. a bold version) and publish it without my permission. Other than that, you are free to use it as you like in any way (mix it with other fonts/ change letters etc. etc.)
If you have questions or comments, you can write to my email: firstname.lastname@example.org
You are also very welcome to show me how you've used the font, as part of the joy creating a font lies in seeing it being used.