The OSPAR Rules of Procedure state:

OSPAR is committed to making as much information as possible publicly available, consistent with achieving other similarly important goals of public policy. The framework for this is set out in Article 9 of the OSPAR Convention.

Following this, OSPAR data made available for download via the OSPAR Data and Information Management System (ODIMS), are licensed according to Creative Commons Zero:

CC0 enables scientists, educators, artists and other creators and owners of copyright- or database-protected content to waive those interests in their works and thereby place them as completely as possible in the public domain, so that others may freely build upon, enhance and reuse the works for any purposes without restriction under copyright or database law.

If a reference to the data origin is required, though this is not a term for data use, the following form can be followed:

Data Source: OSPAR Data and Information Management System, https://odims.ospar.org/(add direct link to dataset or metadata)