From: https://github.com/commanderx16/x16-rom/blob/master/LICENSE.md

The X16 ROM consists of various components with different licenses:

Commercial Licenses
===================
The following components are based on non-open source projects, and their
base code has commercial licenses:

  Component		Subdirectory	Copyright
  ===============================================
  Commodore KERNAL	kernal/cbm	(C) 1983 Commodore Business Machines

  Microsoft BASIC	basic, math	(C) 1977 Microsoft Corp.
  (with Commodore extensions)		(C) 1983 Commodore Business Machines

  GEOS			geos		(C) 1985 Berkeley Softworks

The X16 project has a license to use this code in the context of the X16
computer. If you want to use these components outside of the context of
the X16, please contaxt Cloanto (KERNAL and BASIC) and Click Here Software
(GEOS) for details.


General Public License V3
=========================
The following component is GPLv3-licensed:

  Component		Subdirectory		License
  =====================================================
  MEGA65 KERNAL		kernal/open-roms	GPLv3
  Reimplementation

This component is **not** a part of a default build!


Public Domain
=============
The following components are in the public domain:

  Component		Subdirectory		License
  ===========================================================
  PETSCII charset	charset			public domain

  ISO charset (PXLfont)	charset			public domain

  Keyboard tables	keymap			public domain

  Machine Language	monitor			public domain
  Monitor


3-Clause BSD
============
The following components are under the 3-clause BSD license:

  Component		Subdirectory		License
  ===========================================================
  LZSA2 Decompression	kernal/lzsa.s		3-clause BSD


2-Clause BSD
============
All code outside of the subdirectories above as well as additions to
legacy code are under the 2-clause BSD license.


  Component		Subdirectory		License
  ===========================================================
  BASIC additions	basic			2-clause BSD

  KERNAL additions	kernal			2-clause BSD

  GEOS additions	geos			2-clause BSD

  CMDR-DOS and FAT32	dos			2-clause BSD
  for 6502

  CodeX Interactive	codex			2-clause BSD
  Assembly Environment