New data from the German foundation that processes WikiLeaks' bills show that the document-leaking website has sharply increased its spending as it seeks to professionalize its activities by paying salaries—primarily to founder Julian Assange—and as the organization faces potential legal issues.

At the same time, the Germany-based Wau Holland Foundation says it has collected about €1 million ($1.3 million) in donations in 2010, the year in which WikiLeaks exploded into public prominence thanks to its release of thousands of...