This is a faithful photographic reproduction of an original two-dimensional work of art. The work of art itself is in the public domain for the following reason:

This image of simple geometry is ineligible for copyright and therefore in the public domain, because it consists entirely of information that is common property and contains no original authorship.

This digital reproduction has been released under the following licenses:

I, the copyright holder of this work, release this work into the public domain. This applies worldwide. In some countries this may not be legally possible; if so: I grant anyone the right to use this work for any purpose, without any conditions, unless such conditions are required by law.

In many jurisdictions, faithful reproductions of two-dimensional public domain works of art are not copyrightable. The Wikimedia Foundation's position is that these works are not copyrightable in the United States (see Commons:Reuse of PD-Art photographs). In these jurisdictions, this work is actually in the public domain and the requirements of the digital reproduction's license are not compulsory.