My recollection is that the original prototype was written in Perl, but the oldest commit on github[1] is in C, which is still the language it uses today. The original C version had big contributions from someone other than Brad starting from the third commit (search the git commit log for 'avva'). Definitely still Brad's baby though.

(Disclaimer: I was an early, minor, contributor. It looks like the second commit mentioning me was to fix a bug introduced by my first one, whoops.)

[1] https://github.com/memcached/memcached/tree/32f382b605b4565b...