Luckily I worked out a fairly simple fix. The short of it is that you need to override the default OS X libcurl library, when running the game, with an older version. The newer version one that comes with OS X 10.10.5 will remain in place and work for everything else.
Download, curl v83.1.2
cd /tmp curl -O https://opensource.apple.com/tarballs/curl/curl-83.1.2.tar.gz
Extract the source
tar xvfz curl-83.1.2.tar.gz cd curl-83.1.2/curl
Compile curl with i386 architecture (this is to match the 'Driver: San Francisco' architecture)
export CFLAGS="-arch i386" export LDFLAGS="-arch i386" ./configure --with-gssapi --enable-hidden-symbols --disable-static --enable-threaded-resolver --with-darwinssl --without-libssh2 make
Install the older version of curl in
Launch 'Driver: San Francisco' with the newly compiled older library
cd ~ DYLD_ROOT_PATH=/usr/local/lib ~/Library/Application\ Support/Steam/steamapps/common/Driver\ San\ Francisco/Driver\ San\ Francisco.app/Contents/MacOS/DriverNG
I hope this works for you as well as it worked for me!