This image is authored by Arp. It was uploaded to waarneming.nl and later copied to commons at a time that waarneming.nl did not yet properly support the only really free and unhampered license (CC0 Public Domain dedication) preferred by the author, so it was originally uploaded (here) as CC-BY, but it's not limited in it's use for remixing by that hampered license scheme. It is in fact available as:

Този файл е достъпен под лиценза Creative Commons CC0 1.0 Универсален Посвещение на публичните домейни.

The person who associated a work with this deed has dedicated the work to the public domain by waiving all of their rights to the work worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law. You can copy, modify, distribute and perform the work, even for commercial purposes, all without asking permission. http://creativecommons.org/publicdomain/zero/1.0/deed.enCC0Creative Commons Zero, Public Domain Dedicationfalsefalse