There is no straightforward answer to such a question, as it is not always obvious to indicate how one should count electrons being donated to other groups, or how to correctly partition electrons between nuclei.
In 1978, using ab initio calculations F.A. Momany has computed the Mulliken charges of the atoms of formic acid at the STO-3G level, and compared this to the use of an electrostatic potential. If one only looks at the Mulliken partial charges, this would tentatively answer the question.
The partial atomic charges of the C atom, the C=O oxygen and the OH oxygen are respectively is 0.262, -0.294 and -0.256. So it seems that the C might indeed be donating to both of the oxygen atoms. But one should also consider that the H atom bound to the OH oxygen is also donating some of its electron density to the O: the partial charge of the OH H atom is computed at 0.214. Thus, overall, the C atom is only contributing by a net positive charge of 0.042 to the O atom of the OH group.