Yeah, Mudlet just parses the JSON and builds a gmcp.Whatever table for all gmcp data. You still have to sendGMCP() to fetch skills and rift data (and hack it a bit with Lua logic), but beyond that it's done for you. Super easy.
I'm pretty sure I string match GMCP personally, since it's the simplest to execute, but I have a skills fetch I might be able to make available. GMCP isn't something I'm personally more than a journeyman with.
The UI for Oasys didn't transfer because before I refactored it it was set for hard pixel values instead of percentages. Thankfully with @Irruel's help I was able to…