With certain exceptions a firearm may be made by a nonlicensee provided it is not for sale and the maker is not prohibited from possessing firearms.
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from website linked above.
The above says that a person cannot manufacture a firearm for sale, not that you never can sell it. You can't manufacture it for the purpose of selling it. Big difference in meaning. If they had meant you can never sell it, the would have said "With certain exceptions a firearm may be made by a nonlicensee provided it is not sold..."
Granted, the above is an interpretational issue, but one thing it does not say, nor does any other law or ruling, is that it can't be given away, transferred, willed, etc.
Regarding dzzd questions. There is no requirement for background checks or approval from the BATF for the purchase or completion of lower that is less than 80% complete. Anything above 80% must be purchased from an FFL.
The completion of an 80% into a firearm cannot be done by anyone who would be restricted from purchasing the gun from an FFL. In other words, no felons, no outstanding Restraining/Protection Orders, etc.
Those posts that indicate further dealings with the ATF is required to complete an 80% are either wrong, or they are doing something that requires additional licensing. You are not required to notify ATF, pay manufacturing taxes, have a serial number, register it, or anything else. (Except for any applicable State Laws).
Unfortunately, there is no way around the legalese when dealing with the BATF.