In my ongoing quest to figure out how to let the Salon Weblog server know that former Salon Weblogs no longer using Radio UserLand (which, it turns out, was developed by just the sort of lunatic you’d expect) have been updated, I’ve been able to confirm what Christian mentioned in a comment. It is indeed possible to ping the Salon Weblog server directly from within WordPress and Movable Type when posting an entry (and if posting this entry is noted, that means I’ve gotten it to work). And though TypePad doesn’t support this directly, there does seem to be a workaround.
Assuming that this does in fact work for me in WordPress, I’ll e-mail those I know who are using TypePad with details for their process. For those of you using other Weblog software, I’ll continue to work on a Java application that can be used to manually notify the Salon server of updates.