This is in response to a message from Steffen of ApacheLounge (which distributes Windows binaries of these and other Apache modules), who drew my attention to compilation errors on Windows in both modules. Users of versions 3.1.1 and 1.0.1 on non-Windows platforms have no need to upgrade.
I’ve also made some minor changes to help Apache 2.0 users to build the modules. I don’t know if they’ll still work on Apache 2.0, but at least they now stand a sporting chance. mod_proxy_html 2.5 remains the safe choice for users of Apache 2.0.