Dynamic loading of C libraries

[Richard Stallman]

I talked with our lawyer, and we determined that GCC's technique of
checking for a symbol whose name says "I am under a GPL3-compatible
license" is ok for Emacs and other GNU packages when dynamically
loading libraries at the C level.

So you can implement dynamic loading with the check for that symbol.
If the symbol is not present then the function to load should
report an error and not load it.