.wdl is C-Script and .c is Lite-C, although you could need .wdl and .c for Lite-C. but there's a special paragraph about that in the manual.

http://www.puppenheim.org/
http://www.wuerfels-welt.de
Old Game Tutorial: http://www.puppenheim.org/MITutorial.zip
Free Game Editor: http://puppenheim.org/AlienalsWeihnachtsmann.zip
http://www.puppenheim.org/blender_starting_main_settings.txt