New developers with fresh ideas are always welcome, if you got an idea of what is still missing in ffdshow and you're you want to try to write it yourself you're always welcome to join the ffdshow-tryouts development. You'll be able to commit changes and make them available for testing for many people that way.
If you got good ideas and want to join just use the forums or mail to email@example.com.
You're a builder and want to be able to fix compilation errors or enhance setup scripts or contribute in any other way? Of course you're welcome too!