My Dog's Penis Is Dark Red And "Bumpy", What's Wrong With It?

Is the discharge from the urethra or from the glands nearby?

If it's from the urethra, go see a vet now.

There's one website that indicates that such discharge from the nearby glands can be normal:
www.homevet.com
Another states that *continuous* discharge is adnormal
www.edp24.co.uk

Are all the shots up to date?  Might it be time to take him in anyway?

This is all connected and its root cause is Balanoposthitis. It is basically an inflammation of penis and prepuce. Your dog must be licking its prepuce as well. The greenish discharge is also another symptom of this disease. It occurs due to the growth of foreign particles of dirt and filth that provide nutrition to bacteria and help them to grow and cause this disease. Its examination is very important. Wet its part with dilute potassium permanganate, quaternary ammonium compounds, hydrogen peroxide, and antibiotic steroid combination. Or a minor surgery to remove these lymphoid follicles and other foreign bodies will also help to get rid of this problem.