Your point being? It's been serving sqlite.org just fine for all this time. You seem to be making some pretty big assumptions about security here without actually explaining what your specific concerns are.
If it was written in Haskell or Rust for example you could be more sure about correctness. I believe for something like this, correctness is fairly important. Not to mention you probably wont even lose speed. As for if the code is understandable, it is a 2600 lines of terse-ish C [0]. Do you really think about the entire blob at the same time?