This still leaves Blue Origin with plenty to do. It'll be the "prime contractor" and handle overall program management, engineering (both for systems and the mission), mission assurance and safety. It'll also provide the Descent Element based on work from its Blue Moon lander.
This is an acknowledgment from all parties, not just Blue Origin, that they'll need help if they're going to fulfill NASA's ambitious goal of returning people to the Moon by 2024. NASA itself is scrambling to award contracts for projects that will study the Moon ahead of the landing -- a human-piloted lander is that much more daunting. The alliance potentially saves massive amounts of time, assuming NASA formally chooses their landing system.
All three partners have plenty of directly relevant experience, at least. Lockheed has been working on its own lunar lander design, while Northrop intends to base its Transfer Element on the Cygnus capsules it uses for International Space Station resupply missions. Draper, in turn, is no stranger to Moon missions when it built the guidance computer for the Apollo program. It's a question of whether or not all these companies can come together to produce a Human Landing System on time and with the safety levels NASA needs. The lander's first trip to the Moon will have people aboard, so Blue Origin and friends can't take any chances.