I didn’t know until a while ago that Haiku was the successor of BeOS. Forgive my ignorance, though this triggers my curiosity:
Is Haiku a 100% clone of BeOS and BeOS’s kernel?
Does Haiku use BeOS source codes directly (via reverse engineering)?
I remember my relative used to work on BeOS and it is pretty interesting for me.
Thank you for listening.
No, you should take then clams from news websites saying haiku is the successor to beos lightly 
. Haiku A1 to R1 has/will have binary compatibility with beos* as well sharing the same API as the beos*.
From what I remember Haiku’s kernel is based on newos, and the only beos code in haiku is the code that has been opened up under the MIT license.
*This will not the the case with haiku R2.
The goal (that I know of) are that Haiku R1 will be binary compatible with BeOS r5 + Bone.
But let’s be clear about this.
Haiku will be able to run BeOS R5 applications with a compatibility mode.
Haiku already has more APIs than R5, it has more POSIX compliance, it has better modern hardware support, it has better performance in many ways.
Haiku R1 is not aiming just be equal to BeOS R5, it will surpass it in as many ways as possible while still being able to run BeOS R5 binaries.
The term “Clone” is wrong - it’s misleading.