Can the active player receive free cards in Bohnanza?
Yes, but (as you note) the donations need not be accepted.

From the rulebook, page 5:


  Although trading is preferable to donating, it is often in a player’s
  interest to donate cards rather than keeping them, since cards kept
  must eventually be planted. The active player may donate the two face
  up cards he drew or cards from his hand. The other players may only
  donate cards to the active player and from their hands. Donations
  need not be accepted.