In light of the 0.8.0 release, which requires the additional SKY.CPT file to run Beneath a Steel Sky, we've updated the archive of the freeware CD version to include this file, and while we were at it, updated the data files to the last-known released version of BASS, which should fix some text issues that appear when playing the game in non-english languages.
You can download it from the downloads page (whenever the SourceForge mirrors pick it up), or download the SKY.CPT file separately here.