MPXJ

MPXJ is an open source library (Java, .NET, Ruby) to read and write project schedule data: Microsoft Project MPX, MSPDI XML, MPP/MPT/MPD (98–2019), Planner, Primavera XER, Asta Powerproject/Easyplan, GanttProject GAN, TurboProject PEP, Synchro SP, and others. Actively maintained.