The lead developer changed the license to a much less permissive one because of drama surrounding being credited in modpacks. The dev thinks there are forks that exist solely to sidestep crediting the original mod, I’m not up to date enough on Minecraft modding lore to know if this is true or not.
I’m pretty sure there’s also a fork that branches off of the last GPL commit but I forget what it’s called.
Doesn’t GPL technically require you to attribute the upstream anyway?
The work must carry prominent notices stating that you modified it, and giving a relevant date.
Most open sorce licenses do, not just the GPL. I’m not sure what Minecraft modpackers do. But in the free and open source world, you’ll always find that attribution. Sometimes they have a list who wrote the software and who maintained it for what timespan.