If you really got interest on source code, Search .mq4 instead of .ex4 in Google.
Otherwise, search alternatives if possible.
Even the author release both .mq4 and .ex4, but you try to decompile the .ex4,
You are doing illegal task.
You lose your respect to author.
This is something like that there is a girl wears a dress in front of you.
Well, You pick her dress off and watch the panties without her permit.
Don't quibble that she always wear swimsuit and let you see.