got offer from pariden, demand tribute, and 96 gildars to sweeten up the deal.

much like in the case of exchange research, it unclear, whether they demand tribute from me or offer demand tribute pact, and pay me money.

In first case, why would they give me 96 gildars, if my income per turn is around 5, which means that for 30 turn, they'll get around 30 gildars.

In the latter case, I would understand it as price for peace.

the truth is they demanded tribute. they shouldn't offer me gold - I consider this a bug. secondary the net result is that we have 30 turns of peace, but we have already 50 turn of non-aggression path in progress. demanding/offering tributes shouldn't be allowed if NAP is signed. 

It might be allowed but only if result on relationship would be perceivable by player - ie. there should be comment from a champion advisor "if we sign this pact, we'll increase our relationship from cool to neutral m'lord, but it will costs as 0.5 gildar per season. we'll also be safe from attack from their side for the next 30 seasons".

the same should resolve the research exchange offers. "m'lord, if we sign this pact, we'll share our research, this pact will benefits both parties equally."