Fun fact about Polish copyright law â omitting someone employed to work on something (like a film or a game) from credit list of any kind is illegal unless the contract contains a specific clause that makes the employee agree to anonymous distribution of the work. This is derived directly from article 16 of the copyright law (Ustawa z dnia 4 lutego 1994 r. o prawie autorskim i prawach pokrewnych, Dz. U. 1994 Nr 24 poz. 83 ze zmianami późniejszymi) which makes the right to "mark the work with [your] own name, pseudonym, or [to publish] anonymously" a personal (aka moral) right of the author that is perpetual, inalienable and nonassignable.
XSEED's âcompany policyâ of not crediting people who worked on the games unless they're still employed would thus be a violation of copyrights unless the employee, as an author, agreed to anonymous publishing in the contract.