From the Android Central news report:
Microsoft is forming a team internally under the Microsoft Devices division that will handle the development of the Android OS for Surface Duo going forward. According to my sources, up until now, Microsoft had contracted the OS work out to third-party vendors such as Movial, who had the expertise required to bring Android to life on Surface Duo.
Movial is a software, services, and design engineering company that was working closely with Microsoft on Surface Duo during its prototype and development stages. Microsoft has now acquired the local operations of Movial in Romania, Taiwan, and the USA, and is bringing on-board all the Movial employees that were working on the Surface Duo as full-time employees at Microsoft.
Microsoft is not acquiring Movial as a whole. Movial will continue to operate as a standalone company, with employees at its headquarters in Finland remaining at Movial. SeeNews reports that Movial's Iasi office will become Microsoft Romania's fourth research and development center, as it on-boards 60 employees from Movial in that location.
Apparently Microsoft's own Android apps, including the not-so-obviously in-house Microsoft Launcher and SwiftKey, are already developed within Microsoft. So the Movial involvement was at the OS integration level.
Surface Duo is expected to launch with a Snapdragon 855, 6GB RAM, 64/128/256GB storage, and an 11MP camera with two 5.6-inch AMOLED displays, but - perhaps crucially - without 5G, Qi wireless charging, or NFC (for Google Pay). This recent staffing news might indicate that things are behind schedule or it might just be that Microsoft is looking forward to Duo support with updates and further development.