You're confusing unlicensed with legal I think. It is not allowed to make an intentional radiator, even an unlicensed one, that hasn't been certified to comply with FCC Part 15 limits for the frequency it uses.
More here: www.arrl.org/part-15-radio-frequency-devices
From this doc:
"Low-power intentional radiators: Part 15 rules also permit intentional radiators to operate on nearly any frequency. These low-power intentional radiators are limited to specific field strengths that vary with frequency. The field-strength limits were chosen so that interference is not expected under most circumstances. These devices are certificated."