Version 6.0.1+:

Custom license. The license text can be found here: https://github.com/luisagrether/iDisguise/blob/master/LICENSE.md

Version 5.8.2 and prior:

Creative Commons Attribution-ShareAlike 4.0 International. The license text can be found here: https://creativecommons.org/licenses/by-sa/4.0/