DownThemAll! is comprised of a different parts. The core is open source, licensed under MIT with the interface licensed under GPL-2.0. This means that you can reuse code almost everywhere, while forks of DownThemAll! need to be licensed under the GPL-2.0. Forks need to use their own name and logo however.
Copyright © 2017-2019 by Nils Maier
Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the “Software”), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED “AS IS”, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
Copyright © 2016-2019 by Nils Maier The uikit libraries and assets are licensed under the MIT license.
Copyright © 2017-2019 by Nils Maier Licensed under GPL2.0; see LICENSE.gpl-2.0.txt.
Copyright (C) 2012-2019 by Nils Maier Licensed under Creative Commons Attribution-ShareAlike 4.0 International.
The icon font contains icons from Font Awesome.
See: https://creativecommons.org/licenses/by-sa/4.0/legalcode
Copyright © 2010-2019 by Nils Maier, Stefano Verna.
The DownThemAll! name and logo cannot be used without explicit permission in any derivative work, except in credits and license-related notices.
Using the DownThemAll! logo in personal non-distributed non-commercial modifications of the software and forks is permitted without explicit permission.
Distributing official DownThemAll! releases without any modifications is allowed without explicit permission.
Copyright (C) 2016 by Dave Gandy
License: SIL ()
Homepage: http://fortawesome.github.com/Font-Awesome/
Licensed under the Mozilla Public License 2.0.
The list itself is licensed under the Mozilla Public License 2.0. The javascript library accessing it is licensed under the MIT license.