This license was found in the "random" haskell package (http://hackage.haskell.org/package/random). It is Free and GPL-Compatible. The clause that permits modification, as long as "it does not claim to be a definition of the Haskell 98 Language" can be seen as "prohibiting misrepresentation of the origin" of the modified version, a category of clauses traditionally treated as GPL-compatible.
Code derived from the document "Report on the Programming Language Haskell 98", is distributed under the following license: Copyright (c) 2002 Simon Peyton Jones The authors intend this Report to belong to the entire Haskell community, and so we grant permission to copy and distribute it for any purpose, provided that it is reproduced in its entirety, including this Notice. Modified versions of this Report may also be copied and distributed for any purpose, provided that the modified version is clearly presented as such, and that it does not claim to be a definition of the Haskell 98 Language.