It looks like that's something missing from 2MDC's translation file. The best thing would probably to translate the text, and send the translation to 2MDC, so they can include it in an updated Castellano translation.
The alternative would be to just edit /languages/Castellano/definitions.php, do a search for TermsOfServiceBody in the file, and you'll see the text that needs changing.
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The alternative would be to just edit /languages/Castellano/definitions.php, do a search for TermsOfServiceBody in the file, and you'll see the text that needs changing.
Castellano is Spanish, right?