All of the NASA/JPL-generated SPICE data and allied software are freely available to all U.S. citizens whose tax dollars make the operation of NASA missions and the NAIF activity possible. In addition, NAIF makes these data and software available to everyone around the globe. (There may be government-based access restrictions at some locales.) As such, the global public has free access to exactly and entirely the same data and software that are provided to NASA's solar system exploration projects' scientists and engineers; nothing is held back.
Some foreign space agencies also make their SPICE data freely available to the public from their own archives.
Using SPICE data files—usually referred to as "kernels"—requires the use of SPICE Toolkit software to compute interesting observation geometry parameters such as positions, altitudes, lighting angles, and latitudes and longitudes. Thus, using SPICE data normally requires good programming skills since most SPICE software is in the form of application program interfaces (APIs), often called subroutines or modules, that a user integrates into her/his own application program. Consider reading the SPICE Overview tutorial to get a more complete view of this process.
Members of the public who wish to try their hand at using SPICE data and software may make use of the same training materials NAIF offers to professional scientists and engineers. The primary resources are a set of tutorials and a self-guided training course based on those tutorials and "open book" programming lessons. All of the SPICE Toolkit software is very well documented. You will have to be willing to spend the time to read the tutorials and to try the programming lessons!
One alternative to writing your own program using SPICE APIs is to use NAIF's on-line geometry engine, named WebGeocalc. With this tool a person can make many rather complicated observation geometry calculations without having to write code: one uses a web browser to select the desired computation, select the data (SPICE kernels) to be used, and provide needed command instructions. After pressing the CALCULATE button the results of the computation appear in your browser's window. In some cases the results may include simple graphs. You can read more about WebGeocalc here. But take note: even using this tool requires some understanding of space geometry, and the prospecive user MUST read the "About the Data" webpage linked to from within the tool!
If "hacking NASA" is your thing, poking at this website will not be rewarding since everything produced by NAIF is freely, openly offered right here. This includes exposing folders within which data and software may be found. We realize that exposing folders is generally NOT common practice on websites, but it is intentional here.
Instead of hacking, why not consider learning enough about SPICE data and software to construct some truly novel and useful tools that could be of interest to scientists, engineers and the public around the globe?