few questions
1. how does fps compare to blockland at 1k, 10k, and 100k bricks at equal resolutions
I haven't done much optimization yet, but I have done tests.
At the moment with full terrain+lighting+sprites also being rendered, you can stare directly at 50k close-range bricks and still get ~30fps on my machine. This doesn't really account for the fact that in the end game, bricks out of your field of view or out of range will not be rendered. Even without further true graphical optimizations, playing on maps with a million bricks might not be an issue if only the closest 50k were rendered at any given time.
Edit: I can render the entire golden gate bridge build right next to me (nearly 50k bricks) at about 70fps without terrain and lights.
2. how do you plan on avoiding a takedown notice due to use of copyrighted assets
I can't imagine actually using Blockland's assets in a finished product I give to the public. The only assets I'm using now are the brick stud textures as placeholders and those are trivial to replace. (Unless you count the builds themselves, but I don't intend on distributing them with my game anyway, if you want to import Blockland saves it's trivial to do so yourself)
3. If you're implementing a key system (Which it at least looks like you have), how does it differ from Blockland's rather insecure system?
I haven't even started to think about this.
In fact, I'm not even sure I know how Blockland does this.
I'd probably just have people log in when they start up the game, send the salted+hashed password to my server which compares it to the stored salted hash and then return whether or not the person is logged in.