Where can I find the source code of Ubuntu?

1. Linux Kernel Source Code:

   apt-get source linux-source-3.2.0
   

   Where can I find the source code for the Ubuntu Kernel?

2. Ubuntu Source Code:

   Ubuntu archive

3. Specific Software Source Code:

   sudo apt-get build-dep $package
   

   where package is the program/package's source code you want to adopt.

   Then type:

   apt-get source $package
   

   to get the source for that package.

   For instance:

   sudo apt-get build-dep abiword
   apt-get source abiword
   

The source code for every package in the main and universe archives is in Launchpad, or you can get it by enabling Sources in the Software Properties dialog, and then doing apt-get source $packagename in a terminal, after refreshing the package information.

Source code for packages in the partner repositories is not generally available, as they are mostly not open source applications. This is true for some items available in the Software Center as well.

Software in linux distributions is organized into packages. Each package either contains user facing software like Firefox, or libraries like libasound2 which is required by firefox. If you install Firefox, the apt system will figure out what prerequisite packages exist, will download and install them. Now, these packages are generally distributed as binary files that have already been compiled for a given processor architecture, but the exact source used to compile that version of a package is available via apt-get source firefox.

The vast majority of things in Ubuntu's repositories of packages are open source. But Ubuntu does have a list of approved proprietary software. While this software doesn't satisfy the freedom goals of Ubuntu, they are greatly desired by the community, and provide a lot of value. Examples of this are Skype or Sun Java (now removed). These packages are not listed on the Ubuntu packages site.