Building from source
Simple Sitemap Creator requires the Lazarus IDE (v1.5 atleast) & FreePascal compiler to build.
Firstly grab the source from sourceforge, or if you want to be bleeding edge you can grab the latest from the subversion repository (although the latest commit may not work!).
svn checkout svn://svn.code.sf.net/p/simplesitemapcreator/code/trunk simplesitemapcreator
Windows
The easiest options is to download the latest installer.
FreeBSD/Linux/OSX
There are a few options for UNIX based OS, this is my preferred method.
Download and install FreePascal (FreeBSD/Linux users can install from pkg/ports/yum/apt/etc)
Checkout the Lazarus source from their subversion repo: (Again FreeBSD/Linux users should find a version of Lazarus in their package manager)
svn co http://svn.freepascal.org/svn/lazarus/trunk lazarus
Then build the IDE:
cd lazarus make bigide [FreeBSD] gmake bigide
[Linux/FreeBSD] This will build Lazarus using the GTK+2 toolkit which by default compiles applications to use that toolkit too. If you'd prefer to use Qt4 you'll need to install libQt4Pas from your package manager and build Lazarus like so:
make bigide LCL_PLATFORM=qt [FreeBSD] gmake bigide LCL_PLATFORM=qt
Under Mac OSX it will use the Carbon toolkit by default.
After installation, simply load the IDE, open simplesitemapcreator.lpi from Project menu -> Open Project. Then press Shift-F9 to build the program. The binary will appear in the source directory, probably quite large - you'll want to run strip on that.