Relating to contributors or the role of making contributions; describing something that pertains to those who give or add to something.
From contributor + -ial (relating to), building on Latin contribuere and the agent noun contributor. The suffix -ial emphasizes the relationship to those doing the contributing.
This is the adjective Wikipedia editors use when they talk about 'contributorial disputes'—it's the formal way to say arguments between people fighting over who gets credit.
Complete word intelligence in one call. Free tier — 50 lookups/day.