Right but from the start the Uchiha clan ancestor had those eyes; so it was never a curse; (on naruto wiki it says he inherited the eyes from the sage). yes the curse was from the Uchiha ancestor but not from the eye itself. So tobirama was wrong, or kishi was wrong. However I think the curse altered the sharingan and made it be used to take revenge instead of for love.
No, that's not what I mean. The Uchiha got the eyes from the Older Son, so yes it was inherited. But the way they get it, is like a curse, because it will happen when you lose a loved one whether you want it too or not.
Also, Tobirama said that "they are captured by darkness and turned evil." What he means, is that because their power for love is so great, when they lose a loved one, their feelings towards the loss turns malevolent, basically going really emo, blaming the world and such because they lost a loved one.
From this, they are strengthened from the Sharingan ALONG with their feelings, meaning that their feelings grow immensely as their strength grows as well.
This could also be a reason why Obito is freaking out so much for Rin's death. The darkness captured him, and even though it was a small thing for him to try to destroy the Shinobi World over, his resolve was strengthened by this "Curse" making him hate the Shinobi World more than if he wasn't part of the Uchiha Clan.
That is the "Curse" Tobirama is talking about, and the Sharingan is what they obtain from that loss. That doesn't mean that they didn't obtain the eye from being descendants from the Older Son, it just means that they don't get the eyes until their feelings grow great enough to obtain them.