NAIF / SPICE kernel rules (summary)

Source pages:
- NAIF Rules: https://naif.jpl.nasa.gov/naif/rules.html
- NAIF Giving Credit: https://naif.jpl.nasa.gov/naif/credit.html

Key points relevant to CaptainCalc:
- SPICE kernels placed on the NAIF server may be downloaded and used by anyone.
- Redistribution of SPICE kernels distributed by NAIF is permitted as long as they have not been modified.
- When publishing results, please consider giving appropriate credit to the teams/persons who provided the ancillary data/services.

CaptainCalc ships NAIF kernels (e.g., DE440) as unmodified copies.