These are old versions of Gwydion Dylan. 2.0 is the last CMU release,
and 2.1 is the development version that led to 2.2.

We keep it around because you'll need a binary of d2c to compile d2c,
and there might be a binary of an older version available for your 
platform, but not a current one. You're encouraged to submit your binary
of the current version if you do a build for such a platform.