I want anyone to feel free to improve upon, tweak, customize, hack my work as long as they still give credit but I don't want any of my work to be used in a closed source design.
i don't think that is enforcable...
Let's say you make a system made of an input capacitor , followed by an lm741 in unity gain and a 10k output resistor. And you make a board for that. And you apply open source licence. call this an AC coupled buffer amplifier.
i see your schematic. a bit later i make a board containing just the 741 in unity gain and some connectors. i do not publish schematics , i remove the part numbers and cover the entire block in black goop...
how are you going to sue me ?
you will have to prove i saw your schematic.... good luck on that.
you also will have to prove my circuit was built on , or a mod of yours. ( a 741 in unity gain has been around for 50 years.)
you will also have to buy one of my products, strip it out of its epoxy compound and etch the chip top off to verify it is indeed a 741...
let's say i improve your circuit by swapping the 741 for a way better opamp... add some decoupling , a power regulator and some protection circuitry. i also change cap value so the bandwidth is different
how are you going to prove i built this on top of your design ?
with software this licence trick works as you have the sourcecode and can copy ad-literam large blocks. Also in software the binary fingerprint ( compiled code) may turn out to be identical. this is much harder with hardware.
with hardware ? not so. there is only so many ways to make an ac coupled buffer amplifier... and you can't claim copyright over something that has been done before ...
let's take a harder case :
you build an alarm clock in TTL chips with 7 segment displays.
i take that idea, implement it in an FGPA and add pwm dimming of the LED displays and i don't disclose how it's done.. Howe are you going to prove i copied your design and improved it... let's say i copied your schematic literally and synthesized it in an FPGA. the synthesis and mapping will obfuscate it so it becomes undetectable. and even if you detect it in some way : the logic netlist will be completely different from your ttl chip netlist... the function is the same , the physical implementation not...
if you want to protect the functionality you need a patent. if you want to protect the implementation : that is moot as there is so many ways to skin a cat ...
The fact you threw it out there makes it fair game.