If you want to redistribute and/or modify TeX Live, please see the copying conditions.
To the best of our knowledge, all the software in TeX Live meets the requirements of the Free Software Foundation's definition of free software, and the Debian Free Software Guidelines. Where the two conflict, we generally follow the FSF.
In essence, this means that all the material in TeX Live may be freely used, copied, modified, and redistributed, subject to the sources remaining freely available. (Note: this is not true of all the software in the CTAN snapshot or in proTeXt, which are distributed alongside TeX Live in the TeX Collection.)
Of course, you must not yourself claim copyright (especially a proprietary copyright) on TeX Live just because you redistribute it. Again, see the copying conditions for more information.