The decision to include the TTL library make KiCad a derivative work
under the terms of the AGPL version 3 or later license.
Add both the GPL3 and AGPL3 license text files and add a readme file
about the KiCad licensing. Contributing to KiCad still falls under
the GPL3+ license.
Fixes lp:1797095
https://bugs.launchpad.net/kicad/+bug/1797095