It can be Open Source in practice too, as long as you make sure that your Public Domain dedication is actually effective around the world. The best way to do that could be something like CC0, but CC0 itself is problematic because of its explicit no-patent-grant clause, so it's not recommended to use on software. Instead, licenses like 0BSD or MIT-0 are probably your best bet, practically emulating Public Domain and being officially recognized Open Source licenses.
Comments
It can be Open Source in practice too, as long as you make sure that your Public Domain dedication is actually effective around the world. The best way to do that could be something like CC0, but CC0 itself is problematic because of its explicit no-patent-grant clause, so it's not recommended to use on software. Instead, licenses like 0BSD or MIT-0 are probably your best bet, practically emulating Public Domain and being officially recognized Open Source licenses.