I think they're very good friends, especially since I've heard of two times when David was having marriage trouble and he was living with Jon until things worked out/decisions were made. Once was right after the twins were born and then there was a few years ago when things went south with April. Considering David could easily afford to stay in a hotel, rent an apartment, or buy another house anywhere in the world, he had options besides staying with Jon but chose to be with his friend.

I don't think David wanting to be recognized in a theater environment as a composer of a musical in any way indicates a problem or dissatisfaction with the band or with Jon. He's been around the longest. If he had a problem with Jon he could have left more than 30 years ago. He chose being in a band with Jon over Julliard and I don't think he's ever regretted that.