RE: Dynamics GP Integration
Hi,
GP is customizable in some ways... thru Dexterity code that can be written to add functionalities to the existing system. However, you cannot modify the core code of GP as you don't have access to the source.
For integration to external systems, GP comes with some sort of "API" that is called eConnect library and offers functions to create various transactions in GP
The whole documentation about GP eConnect is available online here :
docs.microsoft.com/.../bb219081(v=msdn.10)
Though it says "GP 2013", the library hasn't changed much since then.
You can also install GP Web Services, which offers some sort of API web calls, but in the end it's the eConnect library that's used underneath as well.
docs.microsoft.com/.../cc534132(v=msdn.10)
Most of the developper doc is up there online.
Good luck.