A large number of founders have done this (in the hundreds now) and I'm not aware of anyone having a problem with it, even with people specifically stating what

A large number of founders have done this (in the hundreds now) and I'm not aware of anyone having a problem with it, even with people specifically stating what they were doing in the US (people however have had problems when they've described YC as an "educational program"). Moreover the visa waiver is used extensively by technology companies, investment banks and consultancies when having foreign employees work out of their US offices for short periods (upto several months). Is it a legally airtight option ? - no. Is it in practice what everyone uses ? - yes.