I'm testing the 2.5.2.1 installer and everything appeared to work until I got to the config test.
For some reason media monitor, pypo and liquidsoap were not running.
I was able to manually start media monitor and pypo but liquid soap continues to crash.
Running sudo airtime-liquidsoap gives me this error - File "/usr/local/lib/python2.7/dist-packages/airtime_playout-1.0-py2.7.egg/liquidsoap/opus.liq", line 3, char 43 before "%": Parse error!
The offending line is -                     ignore(output_stereo(%opus(bitrate = 24, channels = 2, signal="music", application="audio", complexity=10, vbr="constrained"), !source))

I tried installing libopus - same error.
I tried removing the include statement and the surrounding if from ls_lib.liq where the opus file is included.
        %ifencoder %opus
        if type == "opus" then
            %include "opus.liq"
        end
        %endif

and I get Error: no %ifdef to end here!

And ironically googling this led me to a similar issue I had in 2013 which was resolved by upgrading Liquidsoap to a newer version.

The version provided with 12.04 is 1.0 and evidently based upon the post from 2013 1.1.1 is required. So I'm upgrading to Trusty to see if that works.
I'm mostly adding this as a comment for anyone who  might stumble into a similar issue.