Add MIT license and package metadata

LICENSE

@@ -0,0 +1,21 @@
+MIT License
+
+Copyright (c) 2026 Tianyuan Chen
+
+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.

README-CN.md

@@ -193,3 +193,11 @@ CI 会在 Ubuntu 与 Windows 上使用 Python 3.11 和 3.13 执行上述检查
 - 不得绕过 CAPTCHA、身份验证、付费墙或其他访问控制。
 - 将 `not_found`、`invalid_input`、`http_error`、`network_error`、`parse_error`、`missing_data`、`data_error`、`partial`、`blocked` 和 `skipped` 视为不同结果。
 - 在统计、化学信息学或机器学习工作中使用前，核对来源记录与生物学适用范围。
+
+## 许可证
+
+AromaNexus 的源代码与原创文档采用 [MIT License](LICENSE) 授权。
+
+该许可证不会授予任何第三方数据集、网站内容、数据源响应或生成数据集的使用权。
+通过 PubChem、NIST、Pyrfume、M2OR、MFFI、ChemicalBook 或其他来源取得的
+数据，仍分别受各来源适用的条款、许可证及使用限制约束。

README.md

@@ -193,3 +193,13 @@ CI runs those checks on Ubuntu and Windows with Python 3.11 and 3.13. Tests use
 - Never bypass CAPTCHA, authentication, paywalls, or other access controls.
 - Treat `not_found`, `invalid_input`, `http_error`, `network_error`, `parse_error`, `missing_data`, `data_error`, `partial`, `blocked`, and `skipped` as different outcomes.
 - Validate provenance and biological scope before using exports in statistics, cheminformatics, or machine-learning work.
+
+## License
+
+AromaNexus source code and original documentation are licensed under the
+[MIT License](LICENSE).
+
+This license does not grant rights to third-party datasets, website content,
+provider responses, or generated datasets. Data obtained from PubChem, NIST,
+Pyrfume, M2OR, MFFI, ChemicalBook, or other providers remains subject to each
+provider's applicable terms, licenses, and usage restrictions.

pyproject.toml

@@ -1,12 +1,14 @@
 [build-system]
-requires = ["setuptools>=69"]
+requires = ["setuptools>=77.0.3"]
 build-backend = "setuptools.build_meta"
 
 [project]
 name = "aromanexus"
 version = "0.3.0"
 description = "Provenance-aware integration for odorant, flavor-molecule, and olfactory-receptor data"
 readme = "README.md"
+license = "MIT"
+license-files = ["LICENSE"]
 requires-python = ">=3.11"
 dependencies = [
   "beautifulsoup4>=4.12",