Question: Which source has a Cost Free, and an Activity of Some, and an Editor of Markitup?
SQL: SELECT "Open source" FROM "2-13707375-1" WHERE "Cost ( US$ )" = 'Free' AND "Activity" = 'Some' AND "Editor" = 'Markitup';

Question: Which site has a Cost Free and a Editor of jsvi?
SQL: SELECT "Site" FROM "2-13707375-1" WHERE "Cost ( US$ )" = 'Free' AND "Editor" = 'jsvi';

Question: What is the cost of an Open Source that is No?
SQL: SELECT "Cost ( US$ )" FROM "2-13707375-1" WHERE "Open source" = 'No';