Wow, really splitting hairs on this one.
SOURCE:1. The point at which something springs into being or from which it derives or is obtained.
2. The point of origin, such as a spring, of a stream or river. (See Synonyms at origin.)
3. One that causes, creates, or initiates; a maker
according to definition 1 it speaks of from which it derives or is obtained.
DERIVE:1. To obtain or receive from a source;1.Obtain something from (a specified source).
2.Base a concept on a logical extension or modification of (another concept).
So, it can be the point at which something begins(the sun) or something from which it derives, which means that it obtains or receives from an outside source, yet transfers those properties of the source to another object. It is an extension
ORIGIN: 1 rise or derivation from a particular source: as in the origin of a word.
the moon is a derivation of the source(the sun). Is the source of a lake the river, is it the the creeks that make the river, is it the mountains snow melt? is it the rain that falls? each is it's own origin. the rain gets it's origin from evaporation, the mountain gets it's snow and water from the rain, the creeks get their source of water from the mountains and snow and rain, the rivers get their source of water from the creeks, the lakes get their source from the rivers, the lakes in turn feed the evaporation process that makes the rain.
Ever seen one of these oxygen making machines for lung patients? They take oxygen from the air and confine it and contain it to be a source of oxygen to the patient. Is it the source or is the air it divides and gathers the source? just as the machine collects and redirects pure oxygen from the original source of the air, it very much is the source or supply of oxygen to the patient. just as the moon collects and redirects the suns light towards the earth. If the moon were not there to capture and reflect that light, the light would be lost into space. Yet the moon collects it and thus redirects it, thus become a source.
If you have a sparkler(firework) and you light it with a lighter as the source of ignition or heat, the sparkler then contains it's own heat to sustain the fire, yet without the lighter, that sparkler would not have the energy to light itself, thus the original lighter was the source of heat, but then the sparkler had its own energy.
If you take a magnifying glass and collect the light of the sun and start a fire, is it the sun that is starting the fire or is it the refraction of the original sunlight that provides the heat and energy to start the fire? Thus, the magnifying glass isn't the source of the light but by it's properties, it redirects and transfers the energy of the original source thus becomming a source of the newly directed and changed energy. The moon doesn't reflect all the light from the sun, but collects and reflects certain wavelengths, thus it's light is of itself. A blue object is not blue, but it gets it's observable properties by reflecting blue light to our eyes. Therefore we see the source of blue from the object but in reality the blue comes from the sunlight and the object reflects the blue(thus not being blue itself) to us. We see the blue as coming from the object, thus the source, yet really it's source is the blue light from the sun.
I am getting myself dizzy with trying to explain, so I will stop.