Are MakeHuman files free?

Yes. The asset license is CC0. In practice this imposes no restriction on your use of the core assets, be they used through MakeHuman or copied through some other means.

For example you can:

• Use a character model in a closed source game without need for attribution
• Sell a character model
• Take all mesh and target assets and build a character generator of your own, with no restriction on what license that character generator needs to have