On the end-user side, this mostly means an improved bug reporting experience. The submission is easier to fill in, and we provide two templates — one for bug reports and one for feature requests.
For developers, it means simplified contribution, as you can simply fork the GIMP repository, commit changes, and send a merge request. Please note that while we accept merge requests, we only do that in cases when patches can be fast-forwarded. That means you need to rebase your fork on the master branch (we’ll see if we can do merge requests for the ‘gimp-2-10’ branch).
In the meantime, work continues in both ‘master’ branch (GTK+3) porting and the ‘gimp-2-10’ branch. Most notably, Ell and Jehan Pagès have been improving the user-perceivable time it takes GIMP to load fonts by adding the asynchronous loading of resources on startup.
What it means is that font loading does not block startup anymore, but if you have a lot of fonts and you want to immediately use the Text tool, you might have to wait.
The API is general rather than fonts-specific and can be further used to add the background loading of brushes, palettes, patterns etc.