Too much coding? Look at all the effort that goes into the Greasemonkey scripts, which people do for free.
This site can have all the programmers it wants, and for free. (well, a free lifetime membership perhaps).
Indeed a surrender button would have to be reserved for premium members; ESPECIALLY non paying members with only 4 games maximum would be inclined to bail out and just join another game. And besides, people who know they can't win anymore sometimes to unpredictable things; people may hate that when it happens, but it IS an element in the game.
Premium members don't mind if some of their games go down to a crawl ; a surrender button for them is EQUIVALENT to just bailing out of the game and missing turns, but without aggravating everyone else at the lost time. And of course Premium members would rarely bail out in that way, and especially if there is a (slight) points penalty on surrendering then I think it will only be used in exceptional cases.
Note that in chess it's very common to give up when it's clear to everyone how the game will end.
Chess is of course strictly 2 players, so perhaps a more structured way of surrendering the game is needed, i.e. ALL remaining parties would need to agree in the same turn to appoint someone a winner. (so either agree with the surrender, or miss that turn.)
EDIT: And also: SURRENDER is a key aspect of warfare. So it adds realism too. Usually, the person surrendering is expecting/hoping for some kind of benefit to the surrender (like, not being cut into small pieces and fed to the dogs.

) In CC it could be a slightly less loss of points, assuming that the victor accepts the surrender. Any of that would have to be a selectable game option of course.
Just thinking out loud. Cut me in half and fry me to a crisp. (No dogs please)