If it smells "musty" (and if HE is TELLING you that, it is quite possible it is worse than merely "musty") then it should not be used around livestock. Don't feed it; and don't use it as bedding either (because they will eat some of it, and because they will be inhaling all those mold spores)
The only really appropriate use for moldy ("musty") hay is as garden mulch or for composting.
If it were totally-NOT musty/moldy, then although it will lose some nutrition after the first 8 months to a year, it is still reasonable (if you have no better choice) to feed it up to a couple years old although you would want an analysis and you would want to supplement certain vitamins. However *nearly* all the old hay I've ever seen was not in a fit condition to be fed due to moldiness.
I would steer far clear of this stuff you've been offered.
Good luck, have fun,
Pat