There are 2 easy ways to contribute to DDF. They are also great way to get knowledge of DDF quickly.
0: Write some test and increase the coverage.
1: Write an example, which is a lhs library file, inside directory DDF.Sam. The example can probably be turned into test to increase the coverage, so feel free to do that.
But, dont worry if you are decreasing the coverage, we just treat it as some sort of eye-candy.