fuse does not seem to be an open source project, so is there any possibility that general folks can contribute to its code base?
Also, I see that fuse throws some fuse error pages when something goes wrong with the app (crash) can this error page be customized?
We’re working on open sourcing the core parts of Fuse to make it easier for others to contribute. 
(Also, the source code for all the libraries is already accessible of course, since it gets installed together with the tools itself).
The error page you mention is only included in preview mode (not in regular app exports) and can not be customized. You can read about the difference between the two here.
You can of course create custom views for your exported apps if you want to. Depending on what kind of errors you want to intercept and report you may have to dive into a bit of uno code, but if it’s just a basic info screen then you’d implement that in the same way as any other page / view in your app.
Appreciated Great team there! 