How this relates to Open Source Software

Modern science relies to a very large degree on computer simulations, computational models, and computational analysis of large data sets.
These methods for doing science all have underlying theoretical assumptions that are verifiable in principle. For very simple systems, this is nearly the same as verifiable in practice.
As systems become more complex, calculations that are verifiable in principle are no longer verifiable in practice without public access to the code.
It is therefore imperative for skeptical scientific inquiry that software for simulating complex systems be available in source-code form.

Modern science relies to a very large degree on computer simulations, computational models, and computational analysis of large data sets.