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author | Tim-Philipp Müller <tim@centricular.net> | 2013-04-22 23:50:17 +0100 |
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committer | Tim-Philipp Müller <tim@centricular.net> | 2013-04-22 23:50:17 +0100 |
commit | aafce272ea44f9590a0890c1c3c6fc116b6529bc (patch) | |
tree | 32a19d5e0e8b00223b013e3c0e049b0d7ec13781 /README.static-linking | |
parent | ce8cb1f1b398bc798ebdad46ef6c3047de6694cc (diff) |
Automatic update of common submodule
Diffstat (limited to 'README.static-linking')
-rw-r--r-- | README.static-linking | 174 |
1 files changed, 174 insertions, 0 deletions
diff --git a/README.static-linking b/README.static-linking new file mode 100644 index 000000000..6d8299be5 --- /dev/null +++ b/README.static-linking @@ -0,0 +1,174 @@ +================================= + GStreamer Static Linking README +================================= + +DRAFT, April 2013 + + + I. INTRODUCTION + +It is possible to link GStreamer libraries, plugins and applications +statically, both in case of free/libre/open-source software applications +and proprietary applications. On some platforms static linking may even +be required. + +However, distributing statically linked binaries using GStreamer usually +requires additional effort to stay compliant with the GNU LGPL v2.1 license. + +The purpose of this document is to draw attention to this fact, and to +summarise in layman's terms what we believe is required from anyone +distributing statically linked GStreamer binaries. Most of this also +applies to dynamically linked GStreamer binaries. + + + II. DISCLAIMER + +This document is not legal advice, nor is it comprehensive. It may use +words in ways that do not match the definition or use in the license +text. It may even be outright wrong. Read the license text for all the +details, it is the only legally binding document in this respect. + +This document is primarily concerned with the implications for the +distribution of binaries based on LGPL-licensed software as imposed by +the LGPL license, but there may be other restrictions to the distribution +of such binaries, such as terms and conditions of distribution channels +(e.g. "app stores"). + + + III. THE SPIRIT OF THE LGPL LICENSE + +The GNU LGPL v2.1 license allows use of such-licensed software by +proprietary applications, but still aims to ensure that at least the +LGPL-licensed software parts remain free under all circumstances. This +means any changes to LGPL-licensed source code must be documented and +be made available on request to those who received binaries of the +software. It also means that it must be possible to make changes to the +LGPL-licensed software parts and make the application use those, as far +as that is possible. And that recipients of an application using +LGPL-licensed software are made aware of their rights according to the +LGPL license. + +In an environment where GStreamer libraries and plugins are used as +dynamically-loaded shared objects (DLL/.so/.dyn files), this is usually +not a big problem, because it is fairly easy to compile a modified version +of the GStreamer libraries or LGPL plugins, and the application will/should +just pick up and use the modified version automatically. All that is needed +is for the original, LGPL-licensed source code and source code modifications +to be made available, and for a way to build the libraries or plugins for +the platform required (usually that will be using the build system scripts +that come with GStreamer, and using the typical build environment on the +system in question, but where that is not the case the needed build scripts +and/or tools would need to be provided as well). + + + IV. THINGS YOU NEED TO DO + + * You must tell users of your application that you are using LGPL-licensed + software, which LGPL-licensed software exactly, and you must provide them + with a copy of the license so they know their rights under the LGPL. + + * You must provide (on request) all the source code and all the changes + or additions you have made to the LGPL-licensed software you are using. + + For GStreamer code we would recommend that the changes be provided either + in form of a branch in a git repository, or as a set of "git format-patch"- + style patches against a GStreamer release or a snapshot of a GStreamer git + repository. The patches should ideally say what was changed and why it + was changed, and there should ideally be separate patches for independent + changes. + + * You must provide a way for users of your application to make changes to + the LGPL-licensed parts of the code, and re-create a full application + binary with the changes (using the standard toolchain and tools of the + target platform; if you are using a custom toolchain or custom tools + you must provide these and document how to use them to create a new + application binary). + + Note that this of course does not mean that the user is allowed to + re-distribute the changed application. Nor does it mean that you have + to provide your proprietary source code - it is sufficient to provide a + ready-made compiled object file that can be relinked into an application + binary with the re-compiled LGPL components. + + + V. THINGS TO LOOK OUT FOR + +While most GStreamer plugins and the libraries they depend on are licensed +under the LGPL or even more permissive licenses, that is not the case for +all plugins and libraries used, esp. those in the gst-plugins-ugly or +some of those in the gst-plugins-bad set of plugins. + +When statically linking proprietary code, care must be taken not to +statically link plugins or libraries that are licensed under less permissive +terms than the LGPL, such as e.g. GPL-licensed libraries. + + + VI. SPECIAL CONSIDERATIONS FOR SPECIFIC USE-CASES + + + 1. Proprietary GStreamer/GLib-based Application On iOS + +Let's assume an individual or a company wants to distribute a proprietary +iOS application that is built on top of GStreamer and GLib through +Apple's App Store. At the time of writing the Apple iPhone developer +agreement didn’t allow the bundling of shared libraries, so distributing +a proprietary iOS application with shared libraries is only possible using +distribution mechanisms outside of the App Store and/or only to jailbroken +devices, a prospect that may not appeal to our individual or company. So the +only alternative then is to link everything statically, which means the +obligations mentioned above come into play. + + + 2. Example: Jabber on iOS + +Tandberg (now Cisco) created a Jabber application for iOS, based on GStreamer. +On request they provided an LGPL compliance bundle in form of a zip file, with +roughly the following contents: + +buildapp.sh +readme.txt +Jabber/Jabber-Info.plist +Jabber/libip.a [236MB binary with proprietary code] +Jabber/main.mm +Jabber/xcconfig/Application.xcconfig +Jabber/xcconfig/Debug.xcconfig +Jabber/xcconfig/Release.xcconfig +Jabber/xcconfig/Shared.xcconfig +Jabber/Resources/*.lproj/Localizable.strings +Jabber/Resources/{Images,Audio,Sounds,IB,Message Styles,Emoticons,Fonts}/* +Jabber/Resources/* +Jabber.xcodeproj/project.pbxproj +Jabber.xcodeproj/project.xcworkspace/contents.xcworkspacedata +opensource/build/config.site +opensource/build/m4/movi.m4 +opensource/build/scripts/clean-deps.sh +opensource/build/scripts/fixup-makefile.sh +opensource/build/scripts/MoviMaker.py +opensource/build.sh +opensource/env.sh +opensource/Makefile +opensource/external/glib/* +opensource/external/gstreamer/{gstreamer,gst-plugins-*}/* +opensource/external/openssl/* +opensource/external/proxy-libintl/* +opensource/toolchain/darwin-x86/bin/{misc autotoools,m4,glib-mkenums,glib-genmarshal,libtool,pkg-config,etc.} +opensource/toolchain/darwin-x86/share/{aclocal,aclocal-1.11,autoconf,automake-1.11,libtool}/* +opensource/toolchain/darwin-x86/share/Config.pm +opensource/toolchain/darwin-x86/share/Config.pm.movi.in +patches/glib/glib.patch +patches/gst-plugins-bad/gst-plugins-bad.patch +patches/gst-plugins-base/gst-plugins-base.patch +patches/gst-plugins-good/gst-plugins-good.patch +patches/gstreamer/gstreamer.patch +patches/openssl/openssl.patch + +readme.txt starts with "This Readme file describes how to build the Cisco +Jabber for iPad application. You need to install Xcode, but the final package +is built by running buildapp.sh." and describes how to build project, +prerequisites, the procedure in detail, and a "How to Include Provisioning +Profile Manually / Alternate Code Signing Instructions" section. + + + 3. Random Links Which May Be Of Interest + +[0] http://multinc.com/2009/08/24/compatibility-between-the-iphone-app-store-and-the-lgpl/ |