As long as the 1D-2D-3D architecture of D-Flow Flexible Mesh (D-Flow FM) is subject to change, the access to the D-Flow FM code will be limited to a small group of Partners in Development. We anticipate having D-Flow FM in open source for everyone in 2018, but it could become 2019/2020.
Note that our development team is working hard to make all components of Delft3D FM available in open source, both computational engines and Graphical User Interface components (GUI). For now, only DELWAQ,RTC-TOOLS and SWAN are available in open source, which are the computational engines of D-Water Quality, D-Real Time Control and D-Waves, respectively.
The manuals of D-Flow Flexible Mesh and D-Waves can be downloaded here.