Licensing of Haskell code

[Ashley Yakeley]

In article <200305201007.14918.alastair@reid-consulting-uk.ltd.uk>,
 Alastair Reid <alastair@reid-consulting-uk.ltd.uk> wrote:

>    GPL + MIT = GPL      # I think this is true.
>    BSD + MIT = BSD     # This may also be true
>    x + x = x                     # This says that we can delete any duplicates

By "+" I assume you mean "must comply with at least one" rather than 
"must comply with both"?

OK, this may not be immediately practical, but... as contracts, would it 
be possible to express licenses in a Haskell-like language? Didn't Simon 
PJ do some kind of work on this? There seem to be interesting 
covariant/contravariant properties here, for instance, if I require you 
to allow A to anyone who does B, then that is satisfied if you allow 
more than A to anyone who does less than B.

Just an idea anyway.

-- 
Ashley Yakeley, Seattle WA