HACKING: Clarify the intent of the license

HACKING.md

@@ -6,6 +6,27 @@ Although the library uses GLib internally, libfprint is designed to provide
 a completely neutral interface to its application users. So, the public
 APIs should never return GLib data types.
 
+## License clarification
+
+Although this library's license could allow for shims that hook up into
+proprietary blobs to add driver support for some unsupported devices, the
+intent of the original authors, and of current maintainers of the library,
+was for this license to allow _integration into_ proprietary stacks, not
+_integration of_ proprietary code in the library.
+
+As such, no code to integrate proprietary drivers will be accepted in libfprint
+upstream. Proprietary drivers would make it impossible to debug problems in
+libfprint, as we wouldn't know what the proprietary driver does behind the
+library's back. The closed source nature of drivers is usually used to hide
+parts of the hardware setup, such as encryption keys, or protocols, in order
+to protect the hardware's integrity. Unfortunately, this is only [security through
+obscurity](https://en.wikipedia.org/wiki/Security_through_obscurity).
+
+We however encourage potential contributors to take advantage of libfprint's
+source availability to create such shims to make it easier to reverse-engineer
+proprietary drivers in order to create new free software drivers, to the extent
+permitted by local laws.
+
 ## Two-faced-ness
 
 Like any decent library, this one is designed to provide a stable and