On the Raspberry-Pi you can unpack an archive using the 'tar' command.
The following can be used to unpack any of the tar-gnu-zipped (.tgz) files:
tar -xzf name_of_the_archive.tgz
tar -xzf enable_uart_src.tgz
Source code always consists of multiple files and will be unpacked in a directory, executables are unpacked in-situ.
All window files are archived using 'zip' which nowadays is standard available under windows.
Every C source file comes with a Makefile.
To build the program go into the directory and use:
Build GUI (C++)  The GUIs are written using QT4 which requires the source to be written in C++.
To build the program on the Raspberry-Pi you can use the standard gcc compiler.
But you must first install the QT4 development environment.
A link how to do that can be found here:
Tutorial : apt-get install Qt4 on the Rasperry Pi
After unpacking the data go into the directory and type: qmake program_name.pro    followed by typing make.
Thus for the gertbot use: qmake gertbot.pro   After that type make
For the DCC example use: qmake gb_dcc.pro   After that type make
The 'qmake' step wil generate a makefile. Therefore it is only required once or when you make changes to the project (.pro) file. Once you have the Makefile, you can edit the source code files and you can re-build an execuable by using:  make  to compile the programs.
Under windows I use Microsoft Visual Studio 2010 Express. Which can be downloaded for free from Microsoft.
To build the GUI you must also install the QT4 development environment which can be downloaded for free here:
To build the gui, unpack the archive using the standard zip-file extractor which is part of windows. Easiest is to generate a visual studio project file. In every archive there is a batch file for that: make_mcproj_file.bat
First start the visual studio program then load the generated project file which has extension ".vcxproj" Visual Studio Express will read the file and save it as a .sln file