(a) Any interested person or Indian tribe desiring to intervene, to join other parties, to appear as amicus curiae, or to obtain an order in an appeal before the Board must apply in writing to the Board stating the grounds for the action sought. The Board may grant the permission or relief requested for specified purposes and subject to limitations it established. This section will be liberally construed.

(b) Motions to intervene, to appear as amicus curiae, to join additional parties, or to obtain an order in an appeal pending before the Board must be served in the same manner as appeal briefs.