As stefano wrote, Midori definitely is free software.
Both Ubuntu Tweak and Remastersys are distributed under the terms of the GNU GPL. They are free software... but beware of Ubuntu Tweak! One of its main purposes is to ease the installation of proprietary software. If you do not want to search the Web for licenses before installing anything through Ubuntu Tweak, I recommend you to stay away from it! For this reason it will never be in Trisquel's repositories.
I do not know Remastersys but it looks alright (apart from being left unmaintained for four year according to Wikipedia).
