I used the Effective Moisture Penetration Depth algorithm in Energy Plus some time ago, which seemed a more accesible version only for indoor humidity absorption/release (I dont think it accounts for vapour transfer through the envelope). The HAM model is theoretically more accurate, but getting the material inputs to use it seemed imposible back then.
It was a case related to earth construction systems, so even any hygrothermal property for the EMPD model was quite tricky to find.
Implementing the EMPD in GH should be fairly doable through the additional strings input in the Export to OS component, but back then I just did it in E+. If it helps I could look into my old files and share it.
That said, I don´t really know how the EMPD model compares to HAM or WUFI but WUFI´s material library is a huge asset - it´s sad to hear they are not willing to open their API.
Actually, if you are willing to get to the bottom of it, E+ engineering reference explains the calculation procedure and points to this report for validation.