Stephen Henson
The British developer who for nearly two decades was one of a tiny handful of people actually maintaining OpenSSL.
Henson joined the OpenSSL team at its founding in 1998 and wrote much of what makes the library useful beyond the TLS handshake itself: the X.509 machinery, PKCS #12, the command-line tools, and the FIPS 140-validated module that US government buyers insisted on.
Most of it was done in spare time or as contract work. Henson was also the one who reviewed and committed Robin Seggelmann's heartbeat extension on New Year's Eve 2011. When Heartbleed broke in 2014, it turned out that one of the internet's most critical codebases rested in practice on two people, Henson and Andy Polyakov. The Linux Foundation started paying them salaries afterwards — an unusually clear demonstration of how well open source does when nobody funds it.