Hi, sla_erick

maybe you should try following step:
1. unpack the .tar file like this : tar zxvf StepMania-3.9-src.tar.gz
you could google "tar" for more detail of this command.
2. after you unpack the .tar file. goto the folder that contain the file that you unpack. if the code write by qt, you can try this:
qmake -project
qmake
make
if the code write by GTK+ , i think you could find more info that how compile and install with google and maemo.org.

maybe you could find answer in maemo.org after you seach it.