Ghostwriting in the light of Polish regulations – how does the right to authorship look like.

There is no doubt that the right to authorship in one of the most important personal rights of an author. It is non-transferable. There is no possibility to wave it or assign it to other person. 
The practice shows that authorship of a work is often hidden. It applies to books about  celebrities, their diaries or biographies. Those books are sometimes written by professional writers who have greater experience in that matter, or at least with their assistance. However, information about their presence is rarely shown on the cover.

How does it refer to legal provisions? Is it possible to draft an effective agreement which does not reveal real authorship?
Executing the agreement that transfers authorship to another person is contrary to law. This type of agreement is considered to be invalid.
Nevertheless, legal doctrine permits an author to give their consent to identify other person as the author. This consent makes any action legal and any claims aimed to protect personal right ineffective. 

Even though one may not dispose of their personal rights, legal practice allows to conclude an effective contract under which an author is obliged to refrain from exercising their personal rights. According to copyright and contract law an author may be legally obliged to keep their authorship undisclosed. Nonetheless, this commitment may be deemed contrary to other regulations, e.g. regarding obtaining academic degree.