Does Apple still make iMovie HD available to iLife users? When Apple "upgraded" iMovie back in 2008 from its previous version to the completely rewritten program with a star-shaped icon, they kept the previous version available for download.

Currently, I can't find the older version of iMovie on Apple's site. My question is either a) is there still a legal way to get iMovie HD or b) when did it cease to be available?
No. Apple has removed it from the download section of their site as of about January 26, 2009. See: http://www.macrumors.com/2009/01/27/imovie-hd-6-no-longer-available-for-download/

The direct download link in that article now returns a 404 error.