When a dragon shaman (PHB II, 11) gains the ability to project an additional draconic aura from another source (such as the dragon lord prestige class; DM 38), would the new aura use the same bonus as his existing auras? Could he project an aura from each class simultaneously?
The new aura would use whatever bonus is described for it in the text of the source that grants it. In the case of the dragon lord prestige class, it indicates the bonus of the aura. Contrast this with the Draconic Aura feat (DM 16), which indicates that the new aura’s bonus scales with the dragon shaman’s level. Such a character couldn’t project two different draconic auras separately. Each time a character learns a new draconic aura, it’s simply added to the list of options that he has (possibly with a different bonus). A 6th-level dragon shaman/1st-level dragon lord knows six total auras: five from his dragon shaman class levels (each of which grants a bonus of +2) and one from his dragon lord class levels (which grants a bonus of +1).