Open Source Notices

Open source notices and licensing

Squid Proxy Professional includes open source components alongside proprietary software. This page documents the open source notices and the licensing of those components.

GPL notice. Squid Proxy Professional includes a Windows build of Squid Proxy, which is licensed under the GNU General Public License. Source code for the included Squid build and applicable modifications is made available in accordance with the license. The Squid Proxy Professional management console, installer, licensing system, and related proprietary components are separate commercial software.

Source code for the included Squid build

The complete corresponding source code for the bundled Squid build, in the form used to produce the Windows binary distributed with Squid Proxy Professional, is made available so that recipients can exercise their rights under the GNU General Public License.

Squid version7.7, built for x86_64-pc-cygwin. Shipped in Squid Proxy Professional 1.0.0.
Source archivesquid-7.7.tar.gz (5,098,249 bytes), the upstream release tarball from squid-cache.org, unaltered.
Source SHA-256 checksum5b05417d681c3cca275bc48ede12ee50a3e7d60cb47fb94522ee3a66022a8c59
Upstream signaturesquid-7.7.tar.gz.asc, the Squid Project's detached signature. Signed by Francesco Chemolli (code signing key) <kinkie@squid-cache.org>, key fingerprint 29B4 B1F7 CE03 D1B1 DED2 2F30 28F8 5029 FEF6 E865. Verify with gpg --verify squid-7.7.tar.gz.asc squid-7.7.tar.gz.
Alternative requestIf you require the source on physical media or via another delivery method, contact support@squidproxypro.com.

Modifications and patches

Where the Windows build of Squid included with Squid Proxy Professional differs from the corresponding upstream release, the modifications and patches applied to produce that build are made available alongside the source archive.

Patch setsquid-7.7-versioninfo.patch patches src/Makefile.am to compile squid-version.rc (placed at src/squid-version.rc) with windres and link it into squid.exe as a Windows version resource. This is the only change to Squid's build files. Squid's C and C++ source is not modified.
Build instructionsbuild-tarball.sh, run in a Cygwin shell: unpacks the tarball, applies the patch, regenerates src/Makefile.in with automake --foreign src/Makefile, then configures, builds and runs make install-strip. Paths in the script are those of the build machine. Configure settings: 
CFLAGS="-O2 -DNDEBUG -march=x86-64-v2"
CXXFLAGS="-O2 -DNDEBUG -march=x86-64-v2"
--with-openssl
--without-nettle
--disable-strict-error-checking
--enable-external-acl-helpers='delayer file_userip session unix_group'
--without-nettle makes Squid use its bundled base64 and MD5 code. Built against Cygwin's nettle 4.0, Squid 7.7 rejects every base64-encoded credential, so proxy authentication fails.
ScopeModifications are limited to those required for a clean Windows build, packaging into the installer, and integration with the Squid Proxy Professional management console.

Third-party components

In addition to the Squid build itself, Squid Proxy Professional may bundle a small number of supporting third-party libraries and utilities. Each such component remains under its original license. A complete list of third-party components and their respective licenses is provided with the installer and on this page.

Components list
  • Squid Web Proxy Cache 7.7: GNU GPL v2 or later.
  • Cygwin runtime (cygwin1.dll, cygstdc++-6.dll, cyggcc_s-seh-1.dll, cygiconv-2.dll, cygintl-8.dll, cygsasl2-3.dll, cygcrypt-2.dll, cygltdl-7.dll): GNU LGPL v3. Source from cygwin.com.
  • OpenSSL 3.5.x (cygcrypto-3.dll, cygssl-3.dll): Apache License 2.0.
  • zlib (cygz.dll): zlib license.
  • Oracle Berkeley DB 18.1.40 (cygdb-18.1.dll, used by the basic_db_auth and log_db_daemon helpers): GNU AGPL v3.
  • Embarcadero Delphi VCL/RTL, linked into the management console: Embarcadero EULA.
License textsInstalled with the product in C:\Program Files\Squid Proxy Professional\docs\: GPL.txt, AGPL-3.0.txt, THIRD-PARTY-NOTICES.txt and SOURCE-OFFER.txt. The installer also shows the third-party notices and the written source offer during setup.
AttributionWhere required, attribution and copyright notices for third-party components are reproduced in the bundled licenses directory.

Independence and proprietary components

Squid Proxy Professional is an independent commercial Windows distribution and management console for Squid Proxy. It is not affiliated with, endorsed by, or sponsored by the Squid Project.

The Squid Proxy Professional management console, the Windows installer, the licensing system, and other components developed specifically for Squid Proxy Professional are separately licensed commercial software and are not distributed under the GNU General Public License. The terms of the commercial license apply to those proprietary components and are provided at purchase.

The boundary between GPL-licensed components and proprietary components is made explicit in the installed product. Proprietary binaries do not statically link or otherwise combine with GPL components in a way that would extend the GPL to those proprietary components.

Contact for source requests

For questions about source availability, modifications, or the licensing of bundled components, contact support@squidproxypro.com.