How are modifications of the library licensed?

Description

How are modifications of the library licensed?
You can modify Allegro and distribute the modified Allegro under any licence you want, but the original unmodified parts will still be licenced under the Allegro licence. If you offer your modifications to be included in the official Allegro distribution (e.g. by sending them to the Allegro developers mailing list) you automatically agree with licencing the modification under the Allegro licence.