Skyport is licensed under the GNU Lesser General Public License, version 3 or (at your option) any later version (SPDX: LGPL-3.0-or-later).

Full licence text:

• LGPL-3.0: //www.gnu.org/licenses/lgpl-3.0.txt" rel="noopener nofollow" target="_blank">https://www.gnu.org/licenses/lgpl-3.0.txt" target="_blank" rel="noopener noreferrer">https://www.gnu.org/licenses/lgpl-3.0.txt
• GPL-3.0, which the LGPL extends: //www.gnu.org/licenses/gpl-3.0.txt" rel="noopener nofollow" target="_blank">https://www.gnu.org/licenses/gpl-3.0.txt" target="_blank" rel="noopener noreferrer">https://www.gnu.org/licenses/gpl-3.0.txt

Both are included in the mod's source repository as LICENSE and COPYING: //github.com/seanagain/skyport" rel="noopener nofollow" target="_blank">https://github.com/seanagain/skyport" target="_blank" rel="noopener noreferrer">https://github.com/seanagain/skyport

In plain terms — informal summary only; the licence text above governs:

• Play with it, and include it in any modpack, public or private, free or paid. No permission needed and none need be asked for.
• Write a mod that depends on Skyport, and keep your own mod under whatever licence you like. Depending on it does not make your code LGPL.
• Modify Skyport itself and distribute that, and those modifications must be released under the LGPL as well, with source available.
• No warranty is given.