eSpeak NG License Information

eSpeak NG is derived from eSpeak, written by Jonathan Duddington.

MULTI-LICENSE PROJECT:
- Main Software: GPL-3.0-or-later (https://github.com/espeak-ng/espeak-ng/blob/master/COPYING)
- Some Components: Apache-2.0 (https://github.com/espeak-ng/espeak-ng/blob/master/COPYING.APACHE)
- Windows getopt: BSD-2-Clause (https://github.com/espeak-ng/espeak-ng/blob/master/COPYING.BSD2)

Source: https://github.com/espeak-ng/espeak-ng

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                    GNU GENERAL PUBLIC LICENSE
                       Version 3, 29 June 2007

Copyright (C) 2007 Free Software Foundation, Inc. <http://fsf.org/>

eSpeak NG Text-to-Speech is released under the GPL version 3 or later license.

For the full GPL v3 license text, see:
https://www.gnu.org/licenses/gpl-3.0.html

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eSpeak NG Project

eSpeak NG is an open-source text-to-speech system that uses a formant synthesis
method. It is a maintained fork of eSpeak, supporting 100+ languages.

Homepage: https://github.com/espeak-ng/espeak-ng
Documentation: https://github.com/espeak-ng/espeak-ng/blob/master/README.md
License: https://github.com/espeak-ng/espeak-ng/blob/master/COPYING (GPL v3)

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Use in Intelligent Villagers

In the Intelligent Villagers mod, eSpeak-NG is used as:
1. A STANDALONE CLI PROGRAM (espeak-ng.exe) - called via ProcessBuilder
2. A fallback TTS engine when Piper is unavailable

IMPORTANT: eSpeak-NG is called as a SEPARATE PROCESS, not linked as a library.
This usage pattern (CLI invocation) does NOT trigger GPL copyleft requirements.

The mod does NOT:
- Link statically or dynamically to eSpeak-NG libraries
- Include eSpeak-NG source code
- Create derivative works of eSpeak-NG

Pipeline: Text → eSpeak-NG CLI (separate process) → WAV Audio

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License Compatibility with Apache 2.0

GPL v3 is a copyleft license. However, since eSpeak-NG is invoked as a
SEPARATE EXECUTABLE (CLI) and not linked as a library, the GPL copyleft
does NOT apply to the Intelligent Villagers mod.

This is explicitly permitted under GPL v3:
- Running GPL software as a separate program is allowed
- The output (WAV audio) is not covered by the GPL
- No source code disclosure is required for the mod

Reference: https://www.gnu.org/licenses/gpl-faq.html#GPLInProprietarySystem

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Note on espeak-ng.dll in Piper

Piper TTS includes espeak-ng.dll for phoneme generation. This DLL is
distributed under GPL v3. Piper itself is MIT licensed, and the Piper
maintainers have verified compatibility for their use case.

When using Piper binaries that include espeak-ng.dll:
- The espeak-ng.dll remains under GPL v3
- Piper (MIT) can use it as it's a separate component
- Users must comply with GPL v3 for the espeak-ng.dll component

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