# License > License for Bun Bun itself is MIT-licensed. ## JavaScriptCore Bun statically links JavaScriptCore (and WebKit), which is LGPL-2 licensed. WebCore files from WebKit are also licensed under LGPL-2. Per LGPL-2: > (1) If you statically link against an LGPL'd library, you must also provide your application in an object (not necessarily source) format, so that a user has the opportunity to modify the library and relink the application. Bun's patched version of WebKit lives at https://github.com/oven-sh/webkit. To relink Bun with changes: - `git clone https://github.com/oven-sh/WebKit vendor/WebKit` - `bun sync-webkit-source` (checks out the version pinned in `WEBKIT_VERSION` in `scripts/build/deps/webkit.ts`) - `bun run build:local` `bun run build:local` compiles JavaScriptCore, compiles Bun's `.cpp` bindings for JavaScriptCore (the object files that use JavaScriptCore), and outputs a new `bun` binary with your changes. ## Linked libraries Bun statically links these libraries: | Library | License | | ------------------------------------------------------------------------------------------------------------------------------------------------ | -------------------------------------------------------------------------------------------- | | [`boringssl`](https://boringssl.googlesource.com/boringssl/) | [several licenses](https://boringssl.googlesource.com/boringssl/+/refs/heads/master/LICENSE) | | [`brotli`](https://github.com/google/brotli) | MIT | | [`libarchive`](https://github.com/libarchive/libarchive) | [several licenses](https://github.com/libarchive/libarchive/blob/master/COPYING) | | [`lol-html`](https://github.com/cloudflare/lol-html/tree/master/c-api) | BSD 3-Clause | | [`ls-hpack`](https://github.com/litespeedtech/ls-hpack) | MIT (bundled xxhash is BSD 2-Clause) | | [`ls-qpack`](https://github.com/litespeedtech/ls-qpack) | MIT | | [`lsquic`](https://github.com/litespeedtech/lsquic) | MIT (portions derived from Chromium proto-quic, BSD 3-Clause) | | [`mimalloc`](https://github.com/microsoft/mimalloc) | MIT | | [`picohttp`](https://github.com/h2o/picohttpparser) | dual-licensed under the Perl License or the MIT License | | [`zstd`](https://github.com/facebook/zstd) | dual-licensed under the BSD License or GPLv2 license | | [`simdutf`](https://github.com/simdutf/simdutf) | Apache 2.0 | | [`tinycc`](https://github.com/tinycc/tinycc) | LGPL v2.1 | | [`uSockets`](https://github.com/uNetworking/uSockets) | Apache 2.0 | | [`zlib-ng`](https://github.com/zlib-ng/zlib-ng) | zlib | | [`c-ares`](https://github.com/c-ares/c-ares) | MIT licensed | | [`libicu`](https://github.com/unicode-org/icu) 78 | [ICU license](https://github.com/unicode-org/icu/blob/main/icu4c/LICENSE) | | [`libbase64`](https://github.com/aklomp/base64/blob/master/LICENSE) | BSD 2-Clause | | [`libuv`](https://github.com/libuv/libuv) (on Windows) | MIT | | [`libdeflate`](https://github.com/ebiggers/libdeflate) | MIT | | [`libjpeg-turbo`](https://github.com/libjpeg-turbo/libjpeg-turbo) | BSD 3-Clause / IJG / zlib | | [`libspng`](https://github.com/randy408/libspng) | BSD 2-Clause (portions derived from libpng, PNG Reference Library License v2) | | [`libwebp`](https://github.com/webmproject/libwebp) | BSD 3-Clause | | [`highway`](https://github.com/google/highway) | Apache 2.0 | | [`HdrHistogram_c`](https://github.com/HdrHistogram/HdrHistogram_c) | dual-licensed under CC0 1.0 or the BSD 2-Clause License | | [`sqlite`](https://sqlite.org) (on Linux and Windows) | [public domain](https://sqlite.org/copyright.html) | | A fork of [`uWebsockets`](https://github.com/jarred-sumner/uwebsockets) | Apache 2.0 licensed | | Parts of [Tigerbeetle's IO code](https://github.com/tigerbeetle/tigerbeetle/blob/532c8b70b9142c17e07737ab6d3da68d7500cbca/src/io/windows.zig#L1) | Apache 2.0 licensed | ## Polyfills For compatibility, Bun embeds the following packages into its binary and injects them if imported. | Package | License | | ------------------------------------------------------------------------ | ------- | | [`acorn`](https://github.com/acornjs/acorn) | MIT | | [`acorn-walk`](https://github.com/acornjs/acorn) | MIT | | [`assert`](https://npmjs.com/package/assert) | MIT | | [`browserify-zlib`](https://npmjs.com/package/browserify-zlib) | MIT | | [`buffer`](https://npmjs.com/package/buffer) | MIT | | [`constants-browserify`](https://npmjs.com/package/constants-browserify) | MIT | | [`crypto-browserify`](https://npmjs.com/package/crypto-browserify) | MIT | | [`domain-browser`](https://npmjs.com/package/domain-browser) | MIT | | [`events`](https://npmjs.com/package/events) | MIT | | [`https-browserify`](https://npmjs.com/package/https-browserify) | MIT | | [`os-browserify`](https://npmjs.com/package/os-browserify) | MIT | | [`path-browserify`](https://npmjs.com/package/path-browserify) | MIT | | [`process`](https://npmjs.com/package/process) | MIT | | [`punycode`](https://npmjs.com/package/punycode) | MIT | | [`querystring-es3`](https://npmjs.com/package/querystring-es3) | MIT | | [`stream-browserify`](https://npmjs.com/package/stream-browserify) | MIT | | [`stream-http`](https://npmjs.com/package/stream-http) | MIT | | [`string_decoder`](https://npmjs.com/package/string_decoder) | MIT | | [`timers-browserify`](https://npmjs.com/package/timers-browserify) | MIT | | [`tty-browserify`](https://npmjs.com/package/tty-browserify) | MIT | | [`url`](https://npmjs.com/package/url) | MIT | | [`util`](https://npmjs.com/package/util) | MIT | | [`vm-browserify`](https://npmjs.com/package/vm-browserify) | MIT | ## Additional credits - Bun's JS transpiler and Node.js module resolver source code is a port of [@evanw](https://github.com/evanw)’s [esbuild](https://github.com/evanw/esbuild) project. - Bun's CSS parser source code is derived from the [Lightning CSS](https://github.com/parcel-bundler/lightningcss) and [Servo](https://github.com/servo/servo) projects. - Credit to [@kipply](https://github.com/kipply) for the name "Bun".