Open Parties and Claims is similiar to FTB Teams.

It'd be awesome to be able to share advancements with players in my party.

The dev recommends the use of javadoc in the mod's github. Especially the classes OpenPACClientAPI and OpenPACServerAPI seem useful

This issue has been moved to discord: https://discord.gg/UCKjnamDaW
I am much more active there, and it should get more attention there. Thank you for understanding.