The folder contains a readme file, did you read it? It tells you how to compile it. There's also a FAQ, and there's an index file which describes the other files. If you're talking about files in a directory like contrib, did you read the readme.contrib file? Inside the pascal folder in the contrib folder, did you read the readme.txt file?
What if you're writing a program in Pascal and want to use zlib?
I can name a file anything I want, it doesn't mean that it's whatever a website says a certain file extension is for, and it doesn't mean that Windows will open the correct program if I just double-click on it. If I rename a picture file with a .adb extension, does that mean that picture is now a database? If you open one of those adb files in a text editor, do you see a database?