I have released this picture under CC0, the most liberal licensing terms possible. You may use it without any restrictions. You may even use it without attribution.
I have however two requests:
If you use the image, please mention my name Hanno Böck and if appropriate link to my web page at https://hboeck.de/
Write me an E-Mail with a short note why and how you used my image
These conditions are voluntary. You are not required to fulfill them and may still use my images without attribution and without contacting me.
Licensing
I, the copyright holder of this work, hereby publish it under the following license:
to share – to copy, distribute and transmit the work
to remix – to adapt the work
Under the following conditions:
attribution – You must give appropriate credit, provide a link to the license, and indicate if changes were made. You may do so in any reasonable manner, but not in any way that suggests the licensor endorses you or your use.
share alike – If you remix, transform, or build upon the material, you must distribute your contributions under the same or compatible license as the original.