You should get IBPP source code from our project pages on SourceForge. Go to the files section, and download the latest stable set of source. The source code is distributed as a zip archive. Just unzip to a clean directory of your choice. Have the extraction reconstruct the relative directories from there.
The source code is also available in our Subversion repository which you can browse or access using your favourite port of the svn tools. On Windows, if you would like to discover a very nice and well-done Subversion client for Windows, we recommend you TortoiseSVN. This is an excellent piece of software. This Subversion client integrates completely with the Windows Explorer UI. All Subversion interactions are very easy to do and what's more: the SSH functionnality is built-in! Give it a try.
Along the same lines of recommendations, if you look for a superb GUI for administration and GUI based interactions with your Firebird databases, do yourself a favor and discover FlameRobin! (Yes it is build using IBPP for the database connectivity, but there is much more talent to it than just IBPP.)
tests/unixesdirectory and run
make DEBUG=1to build the tests sample application.
tests/bcb6directories for sample batch files and visual projects files for Microsoft and Borland compilers. It should get you started.