Every occasionally I get asked to share plans for L3-G0. I encourage everyone to build things they love with Lego, but sharing the plans is hard. REALLY hard.
L3-G0 had a rough design, however the "plans" don't come close to the as-built model, so there's a lot of work/confusion that would happen if someone started to build another. It'd probably take me a month of hard work to have something decent enough to share. Nothing personal, but I don't have a ton of free time.
In addition to the Lego model, there are many internal bits of other materials that add to the complexity of the build. He has an aluminum and wood frame with laser cut wood bits. Nothing individually that crazy, but this isn't your normal Lego build. You could get away without some of that if you wanted a static version, but he wasn't designed to "stand" without some of that structure.
For the dynamic version he also has 3D printed bricks internally and of course wires and motors and electronics. None of that's a huge deal, but does make things a bit more complicated.
Probably the biggest problem is 16,000 Lego Bricks.
Very specific Lego Bricks.
Think about that. 16 thousand bricks. Big Lego sets are 1-2 thousand bricks. And those are a completely different very specific group of bricks.
So how do you get 16K bricks? There are places that people part out sets like bricklink and ebay.
But lets go back to that number: 16K bricks. Bricklink has 251 million bricks listed right now. But almost all of those are the completely wrong bricks. When I bought bricks for L3-G0, I ended up buying several kinds for which I bought all of the only bricks of that shape/color available.
Now lets consider what happens if I post the plans. Obviously 10 kids are going to ask dad (or mom) to help build him. If word got out, then it's 100 or 1000 or more. Lego sells 7 sets a second. A quarter billion a year. Presumably 0.001% of those would consider building a Lego R2 instead (or in addition). That tiny number would be 2,000 builds started a year. Let's pretend I'm way off and it's only 20.
Lets look at Bricklink again. Take those 16K bricks times 20 people. That's 320K very specific bricks. That is a HUGE number. Buying the bricks for one L3-G0 distorted the market price of some bricks for a year.
I just looked at one of the common bricks. There are enough for make 2 or 3 Artoos on sale right now. Most of those however are in small lots, which is going to make shipping fees prohibitive. Supply and demand would do the rest. 10 people trying to make Artoo would cause the price of those bricks to skyrocket. Instead of asking $3,000 for the bricks, you'd be looking at more like $10,000 or $25,000. So most of the people that started wouldn't have a chance of finishing.
Worse, look at the Lego clubs and exhibitions around the world. Where do they get their bricks? What if someone wants to build a really cool white castle? Then we've totally messed up their ability to get bricks as well.
All that sounds pessimistic, and, to be frank, it sounds like I'm making excuses for not wanting to share the plans. Mostly though I don't have the time to create usable plans, and I don't want to set up a bunch of kids for failure.
At this point our best bet is Lego Ideas. You may want to follow me there... https://ideas.lego.com/projects/63519 is another project I tried.