Is JME3 going to support Fog? Is it going to be a separate state like it was in JME2?
Is there a way to add glEnable(GL_Fog) and friends without changing the core code (LWJGLRenderer) of JME3?
May be something like "CustomState" that has apply(Context) method that may directly invoke OpenGL API?
jME3 will have support for fog, yes. It's in the issue tracker: http://code.google.com/p/jmonkeyengine/issues/detail?id=64
glEnable(GL_FOG) won't work, because jME3 uses shaders.