The simple answer according to Debian bug #496497 is that Apache 1.3 has been removed.  Debian Etch appears to be the last distribution to support it.

To me, this is a surprise.  Surely Apache 1.3 is still used heavily in production around the world.  The possibility that it could be at this point of abandonment—the point of not even offering it in packages—didn’t even occur to me.  That’s why I wasted so much time trying to “un-break” my installation.

So in short, if your code base relies on Apache 1.3 and you upgrade from Etch, you’re out of luck.  You need to roll back, or possibly compile and install everything by hand, or start looking at migrating from Apache 1.3 to Apache 2.0.  Bug #482648 offers a temporary workaround which I’ve not yet tried.

I have mixed feelings about this.  In a way it’s probably good that the migration from 1.3 to 2.0 is being forced upon us.  In another way though, how does one propose this migration to higher business powers in a way that doesn’t sound like a complete waste of resources?

At worst, managers reject the migration and developers are stuck with Etch.  But then with the exception of backported packages, all future improvements to Debian are essentially immaterial.  Should a code base ever lock things down to that degree?