What is not allowed is to try to prevent others from further sharing any version of GNU Emacs that they might get from you. The precise conditions are found in the GNU General Public License that comes with Emacs and also appears following this section. One way to get a copy of GNU Emacs is from someone else who has it. You may also receive GNU Emacs when you buy a computer.
Computer manufacturers are free to distribute copies on the same terms that apply to everyone else.
These terms require them to give you the full sources, including whatever changes they may have made, and to permit you to redistribute the GNU Emacs received from them under the usual terms of the General Public License. In other words, the program must be free for you when you get it, not just free for the manufacturer. An order form is included at the end of manuals printed by the Foundation. If you find GNU Emacs useful, please send a donation to the Free Software Foundation to support our work. Donations to the Free Software Foundation are tax deductible.