I have been involved in an argument on a mailing list with regards to the legal nature of copyleft licences such as the GPL. This is a bit of a pet peeve of mine (and talking to other lawyers, it seems like I'm not alone in this). This is the fact that in Free Software circles there is a mantra stating that "the GPL is a license, not a contract". An example of this can be found here. I must admit that this artificial distinction drives me up the wall. As far as I can see, Eben Moglen is the one person who came up with this distinction. He explains it like this:
"The word 'license' has, and has had for hundreds of years, a specific technical meaning in the law of property. A license is a unilateral permission to use someone else's property. The traditional example given in the first-year law school Property course is an invitation to come to dinner at my house. If, when you cross my threshold, I sue you for trespass, you plead my 'license,' that is, my unilateral permission to enter on and use my property.The problem with this interpretation is that despite protestations to the contrary about the practice being an "artifact of twentieth-century practice", a licence is still a contract if it fulfils contract formation requirements. The above quote rests on a specific view of contract formation. Contracts require offer, acceptance and in some places consideration (reciprocity). The error in Moglen's explanation is that he is assuming that a contract can only be formed with consideration, which is not the case in a large number of countries of the world that have civil or mixed legal systems (Scotland for example). Contracts in those countries do not require a promise of payment, as specified by Moglen, which then allows unilateral promises and licences. To assume that American contract law applies everywhere seems a bit odd.
A contract, on the other hand, is an exchange of obligations, either of promises for promises or of promises of future performance for present performance or payment. The idea that 'licenses' to use patents or copyrights must be contracts is an artifact of twentieth-century practice, in which licensors offered an exchange of promises with users: 'We will give you a copy of our copyrighted work,' in essence, 'if you pay us and promise to enter into certain obligations concerning the work.' With respect to software, those obligations by users include promises not to decompile or reverse-engineer the software, and not to transfer the software. "
Why would anyone want to make a distinction between a contract and a licence? There are some useful procedural reasons to identify a copyright licence in some jurisdictions. For example, there may be different legal effects if a contract is a licence, or sale of goods, or sale of services. But those three are still contracts!
As far as I can tell, Moglen declares that he has a problem with the global variability of contract law. He says in an interview with Kathy Bowrey (thanks to David Berry for the link): "This is the very reason why I have resisted contractualisation completely because contract law is totally non uniform around the world." With all due respect to Prof. Moglen, it is not up to him to decide if contract law applies to a licence, it is up to the courts. I find a part of the interview very telling. Here Moglen says:
"So all that I do is bring an infringement action. It is the defendant's responsibility to prove license and the only credible license for the defendant to plead is my license, because code is not otherwise available except under that license."That is a dangerous position! Firstly, how do you prove that the user is under a licence other than by contractual law principles? Secondly, this argument would seem to suggest that any user of copyright works can be taken to court, and only then they can prove that they actually had a licence to use the work. Imagine the same paragraph above being said by Bill Gates and not by Eben Moglen, and you will get why this is such a dangerous position! As a colleague pointed out to me, according to this view, all use is a priori infringement until proven otherwise.