I think not. Anonymous sperm donors typically help women or couples conceive when they otherwise could not. While most are probably paid for their service, they are doing something kind for others regardless if that is part of their motivation or not, and the legal guardians are aware that they will be fully and solely responsible for the child.
In the unfortunate occurrence where the parent(s) died after birth, the anonymous donor should still not be required to divulge identity or take responsibility for the minor child.
In this case, the child is the result of a legal contract, and not the result of loving or lustful relations, and some protection should be provided for the anonymous donors, if society deems their service to be a desired one, in order to encourage this desirable behavior, which seems to be the case.
Regards,
Jim