In SQLServerPlatform the default length for a VARCHAR declaration is set to "255". But according to the SQLServer documentation from Microsoft the default length is "1", if omitted in the declaration.
See remarks: http://msdn.microsoft.com/en-us/library/ms186939.aspx
Also the default length is hardcoded in the "getVarcharTypeDeclarationSQLSnippet" method which in my opinion should be evaluated through "getVarcharDefaultLength".
I don't exactly know if the current implementation is intended, otherwise it should be fixed. I would then create an PR if desired.