pgAdmin is available subject to the terms of the licence. pgAdmin is developed using a number of GIT repositories to hold the source code. Access to the repository is available through a web interface or using your favourite GIT client. Under Windows, we recommend using TortoiseGIT, which is free software.
To checkout the source from the command line and get started, you might use commands such as shown below on a Linux or Unix system. For further details, please see the source code build instructions.
git clone git://git.postgresql.org/git/pgadmin3.git