Are there any alternatives to The CMU Pronouncing Dictionary, commercial or open source?
I don't believe the answer is definitively "no," but I do know that CMU is the most popular pronouncing dictionary in my anecdotal experience. I believe it is open source so if it's missing something, perhaps you could find a way to add it (or request it be added).
Barring that, I would check with the folks at Language Log. They deal a lot with phonetics.