This is the embed code for the ee_freeform_composer_template: {embed="_includes/.form_columns" column_count="{composer:column_total}"}

ee_freeform_composer_template_include

{if embed:column_count == 1}
  twelve columns
{/if}

{if embed:column_count == 2}
  six columns
{/if}

{if embed:column_count == 3}
  four columns
{/if}

{if embed:column_count == 4}
  three columns
{/if}

Updated slightly for Foundation 5. You could also add large-X classes as well if needed.

{if embed:column_count == 1}
  small-12 columns
{/if}

{if embed:column_count == 2}
  small-12 medium-six columns
{/if}

{if embed:column_count == 3}
  small-12 medium-four columns
{/if}

{if embed:column_count == 4}
  small-12 medium-three columns
{/if}