As others have suggested...
Driftwood will release tannic acid, often referred to simply as tannins, which turns the water a tea color. Different wood will release a different amount of tannins. Since these tannins are an acid, they will also lower the PH value of an aquarium.
Green water is typically caused by free floating algae. I would suspect that the driftwood had some algae in/on it and from there it began free floating and thriving. Natural sunlight is the biggest contributor to free floating algae thriving. Phosphates, as mentioned, are also a strong contributor.