I'm planning on using TIC-80, and I've been making an entity/component framework loosely based on Monocle (the framework used by Celeste and Towerfall). It has no gameplay-specific code and is really just a big collection of utility classes. It's been mostly an excuse to get my head around Squirrel.
Is it within the rules to copy/paste this into a new file when the jam starts, or will I need to write everything from scratch? It's not really any different to using an established framework in another engine.