A.4.1 Is the SSH or Telnet code available as a DLL?
No, it isn't. It would take a reasonable amount of rewriting for this to be possible, and since the PuTTY project itself doesn't believe in DLLs (they make installation more error-prone) none of us has taken the time to do it.
Most of the code cleanup work would be a good thing to happen in general, so if anyone feels like helping, we wouldn't say no.
See also the wishlist entry.