Technically none of those are the same as the MojoMeter and both of the VU-Meter based ideas are far more simplistic - but still require a decent knowledge of working with electronics.
The MoJoMeter is complete - it's not a kit, you just plug it in. It's a more advanced design and doesn't require any fiddling around and trying different parts to get things right.
Sure - you could invest over $20 in parts and make something similar. Why? We've done it for you - so you don't have to spend time doing it yourself.
However if anyone else is offended that Joe and I have done something cool and want to sell them - feel free to post.
Kermit