Generated BOR programs can only be edited in BOR

What causes this issue?

The program includes the implementation of a business object type.
These programs may only be maintained via the Business Object
Repository (Transaction SWO1).
The object type name can be seen as a comment in the first line of the
object type implementation.

System Response

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

How to fix this error?

Error message extract from SAP system. Copyright SAP SE.