12 years to clean up? That must be worse than starting from scratch.
OTOH what one gets by going this way is a community of users, and therefore it will still beat Hurd 1.0 to completion. Starting an ERP from scratch without funding as a multi-vendor effort would lead to something that would never be released.
But you should see the legacy code. The code we forked from was a textbook of how not to write (secure, maintainable, bug-free, etc) software.