It is ghc's optimised InstalledPackageInfo parser that needs updating.

rolling back:

Fri Dec 12 18:36:22 GMT 2008  Ian Lynagh <igloo@earth.li>
  * Fix Show/Read for License
  We were ending up with things like
      InstalledPackageInfo {
          ...
          license = LGPL Nothing,
          ...
      }
  i.e. "LGPL Nothing" rather than "LGPL", which we couldn't then read.

    M ./Distribution/License.hs -2 +14