Mike Kaply pointed out a blog post on customizing reporter.
For the record most changes can be made without actually touching code, simply by including the correct preferences. This is done intentionally so that upgrading later on doesn’t involve complicated merging of your changes into an updated code base.
To point reporter to an intranet server, the pref you need to use is:
extensions.reporter.serviceURL
To show a custom privacy policy, just point this preference to the page of your choice:
extensions.reporter.privacyURL
Or to not show it all, just default this pref to true:
extensions.reporter.hidePrivacyStatement
For Firefox 3.0 it will no longer use SOAP, instead it will use xmlHttpRequest since SOAP support won’t ship in Firefox 3.0. It’s also easier to implement on the server side.
At one point I half-implemented a proxy service that once installed would capture reports sent to it that matched a given list of hosts, and forwarded all the rest to reporter. Theoretically it would be even easier these days.