Sap dripping from Douglas-fir trees is a common symptom with a variety of possible explanations. This symptom is often referred to as "resinosus". One or just a few high-volume resin flows down low on the trunk often indicate a root disease or wood rot fungus. Numerous small flows higher up on the trunk may be symptoms of bark beetle attack.

Your photos appear to be higher-volume flows such as those resulting from root diseases or trunk rot. Oftentimes trees with such afflictions can hold off the disease and remain relatively healthy for decades as long as the tree is otherwise healthy with a vigorous crown. If the foliage appears to be declining - thinning out, turning yellow or dying back - that is a sign that the tree is losing the battle with root disease or other problem and is likely to continue to decline.