Let's say if company A developed an electronic product. A published the product's datasheet on its website free to the public, copyright of the datasheet is owned by A. One part of the datasheet is the schematics of the product.
Is it fair use, if company B develop a digital simulation model (a software program) and make it free to public, that does not contain A's original schematic, but contains rewriting of the schematic into a digital form?
Copyright does not apply.
From the description, company B is simply copying the circuit design. Copyright would only protect that specific schematic drawing of the circuit. The design of the circuit, i.e. how chips and resistors are logically connected, is utilitarian and is not protected by copyright.
Instead, patents may apply. If the original datasheet wasn't public, then trade secret laws may also apply. Trademarks may also apply to product names, so they will have to be used carefully.
