LICENSE.txt

Copyright Edward Brekelbaum

This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program.  If not, see <http://www.gnu.org/licenses/>.

----
TLDR; This code is available under GPL v3 (or later, if you like).

TLDR GPL; Don't be a jerk.  If you give (or sell) someone a binary, give
them the source code you used to make that binary.  Don't frustrate their
build by using hardware private keys and stuff.  Play nice.