The rights to a screenplay are typically owned by the person or persons who wrote the screenplay, unless they have signed a contract transferring those rights to someone else. In the film industry, it is common for screenwriters to transfer the rights to their screenplays to producers or studios in exchange for payment.
Once the rights to a screenplay have been transferred, the owner of the rights has the exclusive right to produce, distribute, and sell copies of the screenplay. They also have the right to make any changes or adaptations to the screenplay, as long as the original writer is credited for their work.
If a screenplay is based on an existing work, such as a book or a play, the rights to the screenplay may also be subject to the rights of the original work. In these cases, the screenwriter may need to obtain permission from the owner of the rights to the original work in order to use the material in their screenplay.