ECL is distributed under the GNU LGPL, which allows for commercial uses of the software. A more precise description is given in the Copyright notice which is shipped with ECL.
---- BEGINNING OF COPYRIGHT FOR THE ECL CORE ENVIRONMENT ------------
  Copyright (c) 2019-2024 Daniel Kochmański and Marius Gerbershagen
  Copyright (c) 2015-2018, Daniel Kochmański
  Copyright (c) 2000-2013, Juan Jose Garcia Ripoll
  Copyright (c) 1990, 1991, 1993 Giuseppe Attardi
  Copyright (c) 1984 Taiichi Yuasa and Masami Hagiya
	      All Rights Reserved
  ECL is free software; you can redistribute it and/or
  modify it under the terms of the GNU Lesser General Public
  License as published by the Free Software Foundation; either
  version 2.1 of the License, or (at your option) any later version.
  This library 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
  Lesser General Public License for more details.
  You should have received a copy of the GNU Lesser General Public
  License along with this library; if not, write to the Free Software
  Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
  PLEASE NOTE THAT:
  This license covers all of the ECL program except for the files
	src/lsp/loop.lsp	; Symbolic's LOOP macro
	src/lsp/pprint.lsp	; CMUCL's pretty printer
	src/lsp/format.lsp	; CMUCL's format
  and the directories
	contrib/		; User contributed extensions
        examples/               ; Examples for the ECL usage
  Look the precise copyright of these extensions in the corresponding
  files.
  Examples are licensed under: (SPDX-License-Identifier) BSD-2-Clause
  Report bugs, comments, suggestions to the ecl mailing list:
  ecl-devel@common-lisp.net.
---- END OF COPYRIGHT FOR THE ECL CORE ENVIRONMENT ------------------
Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.3 or any later version published by the Free Software Foundation; with no Invariant Sections, with the no Front-Cover Texts, and with no Back-Cover Texts. Exact text of the license is available at https://www.gnu.org/copyleft/fdl.html.