No catch, they only want to "capture" SV engineers. So if you work for Google in San Francisco and you convince your bosses you can work 3 months from Helsinki legally and hopefully for Finland form a company there or meet a Finn and bring them back to the US with you.
Mr Johnny Boy, a Google engineer with 10 years of experience goes to Helsinki with this program, he loves the place but 3 months later he returns to San Francisco, 6 months later he quits Google and founds a start-up. He remembers about Linus, a young Finn who he met there and who is a OS wizard. He hires Linus as a his # 1 employee.2 years later the company is doing great so they open their European branch in... Helsinki.
I called the programme organizer. The catch is that you need a job in the US that is willing to let you work remotely. There might be tax issues if u r willing to relocate ur permanent residence.