Single line, no assumptions about data previously stored, no invalid CSV with quotes getting the entire line and no useless spaces in the beginning of each line:

echo "name,creditcard$(wget -qO- https://gist.githubusercontent.com/jorin-vogel/7f19ce95a9a84... | jq -r 'map(select(.creditcard != null) | .name + "," + .creditcard)' | sed -E -e 's/\]|\"|\[| {2,}|,$//g')" > $(date +"%Y%m%d").csv