Recursive Contracts: Keeping Software Liberated

Simply put, contracts are said to place rights and obligations upon the contracting parties. This is simple enough i.e. I promise to do X if you promise to do Y…

I’ve struggled a bit to get to grips with ‘copyleft’ software licenses (check previous post), which aim to keep a piece of software ‘liberated’.

The copyleft license achieves this by obliging the recipient of the liberated software copy to place similar obligations on recipients of future copies/modifications. So in effect, by contracting under the terms of the copyleft license, the recipient is restricted as to the terms under which he can contract in future dealings involving the liberated software.

It was hard for me at first to grasp that I was dealing with a creature of contract – which I saw somewhere on Wikipedia referred to as ‘recursive contracts’.

I guess a straight forward way to ‘set up’ a recursive contract may be as follows. Suppose you are dealing with an item (Y). And you have a set of terms (X), relating to the deal involving Y, which you intended should recur in any future deals involving Y. Then this recurrence obligation may be established by including into X a final term which iterates that X should be present in the terms of any future dealings involving Y.

(Note that the key point here is that the term which iterates the recurrence of X is in X itself).

This approach appears to be used in to create the recurrence aspect of the GPL license (a popular copyleft license) where the key term appears under section 5(b) which states that:

“The work must carry prominent notices stating that it is
released under this License and any conditions added under section
7. This requirement modifies the requirement in section 4 to
“keep intact all notices”.”