[egypturnash]

By using the simple in-game 3D modeller, or by using an external 3D modeller and importing meshes. Plus time writing or adapting scripts in SL's scripting language, if there's any interactivity needed.

It is a similar amount of effort to what goes into making the equivalent object in a 3D game, and if you have the skills and the time, sure, clone other people's stuff, or make your own riffs on them!

[cosarara]

Wouldn't it be possible to rip the mesh of the existing object directly out of the game client's memory? And then import it again as a new (copyable) object.

[hhh]

In the SL world, this is called copybotting.

[Raph_Koster]

That would be because of a tool called CopyBot which came out in 2006.

https://www.raphkoster.com/2006/11/15/copybot/

[Animats]

Yes, but if you try to sell it, that gets noticed, and the copier has DMCA problems.

Also, scripting is entirely server side, so that's not copyable.