Items exchange

[Lionette]

Is it possible to just give items (or even doors) away in exchange for nothing?

E.g. when one player is fighting for the winning level and there is a thief at the table who could have backstabbed him, but he doesn't have any cards. Can other players just give him cards in exchange for nothing?

And another question on a very similar topic: can one player help another in a combat if he won't get anything out of it for himself? I.e. help in exchange for nothing?

We've been arguing about it for quite a while, so official ruling would come in very handy.

Thanks!