Zend certified PHP/Magento developer

What are the constraints for lacking encoder support in FFmpeg?

According to the documentation, there are several video and audio codecs with missing encoder support.

Is this typically because:

A) The encoder is copyright protected.

B) The encoder implementation is unknown (closed-source).

C) No one has so far needed or wanted to implement an FFmpeg version of the encoder.

From reading FFmpeg License and Legal Considerations it is not clear to me whether A is a concern or not for adding a new encoder to FFmpeg. If C is the case and A and B are not a problem, is my only option to get support for a missing encoder in FFmpeg to implement it myself or can I raise a suggestion to a developer somewhere for upcoming features?