Since starting in 2003 as a side-conversation at a conference on the difficulties of transferring gridded data between hydrographic processing packages, the Open Navigation Surface project has been developed by the Open Navigation Surface Working Group, comprising government, industry, and academic partners, on a volunteer basis. The Bathymetric Attributed Grid (BAG) data format has gone on to be supported in many hydrographic data processing packages, and elsewhere, including commonly-used packages such as GDAL and tools that use it (such as ArcGIS, QGIS, Global Mapper, etc.). It also formed the original basis for the IHO S.102 standard for gridded bathymetry. Early in the process, the working group contributed code to implement a default library to read and write the developing data format so that new ideas could be tested, and new adopters would benefit from a reference implementation that makes concrete the assumptions and practices inherent to the format. Over the course of 15 years, however, the source code had been modified and extended many times, and was beginning to show its age. The working group have therefore begun the process of modernizing the application programming interface for the library, with particular emphasis on modern coding practices such as continuous integration, embedded documentation, and good object design. This paper describes the upcoming changes to the project, the basis for the design choices, and the implications for the user community. It also considers the benefits and challenges of maintaining a common, open-source data format with volunteer effort in a small community.