Data retrieved from the Mikulski Archive for Space Telescopes (MAST) are part of the public domain and need no explicit permission for use, with the exception of proprietary data. We take care that these proprietary data are only provided to those who have proprietary rights. No explicit permission is needed for the use of MAST tools. Please acknowledge NASA and MAST when using data retrieved from MAST.
The NASA website hosts a large number of images from the Soviet/Russian space agency, and other non-American space agencies. These are not necessarily in the public domain.
The SOHO (ESA & NASA) joint project implies that all materials created by its probe are copyrighted and require permission for commercial non-educational use. [2]