There was no reason to write it in C++ or worry about the difficulties of distributing an interpreter in the first place. There were good tools already. Stepping out on a limb and doing it with Erlang was unnecessary. I thought the thread was fairly obvious.
I'm unclear about what you mean by "unnecessary". In the strict sense, rewriting the software at all was unnecessary; in the very strict sense, writing it in the first place was unnecessary.
My best guess at what you mean is that they incurred unnecessary risk by rewriting it in Erlang as opposed to some more mature language, but even then I'm not certain what would be meant by "risk", given that it's an open-source project that is distributed for free. In that context, it wouldn't be a business risk in any sense (particularly given that one could just decide to scrap the rewrite if it was turning out poorly).
Might it have been easier in Python or Perl? I have no idea, but it seemed to work out well enough in Erlang, so Erlang would appear to qualify as a "good tool" in this case, at least.
