Nah, in modern flight search, ITA & Vayant take all the raw flight data like schedules, fare rules etc which they buy from companies like OAG and Innovata & IATA. GDS increasingly are nothing more than a source for cacheing prices when a 'direct connect' connection to the airline is not available or where the end consumer (an ota or travel agent for example) will be purchasing via GDS. Certainly no GDS has tech that does open ended real time Graphed queries like Google Flights, Adioso's Wingtip, Vayant, Skyscanner can do
The cached prices are the hard part of the search though (anyone with a licence to schedule data from Innovata or OAG can build a tool that searches for "all return flights from California to Europe in summer"). In theory it should be possible to grab current price/availability for that set of flights from a GDS and filter it to give "all return flights ... under $1500" (minus some LCCs that don't accept GDS bookings) which is the more interesting part of the problem from the consumer's point of view.
Presumably if Adioso are finding it worthwhile building their own price scraping/caching engine the GDS companies aren't willing to allow their systems to be [affordably] queried on that kind of scale. I'm just wondering whether they're claiming it's impossible for technical reasons, IP reasons (they sell price data back to the airlines) or just weren't willing to quote Adioso an affordable rate.
