As far as I know, publishing someone's content as your own is plagiarism. Or does the Twittersphere have a different set of rules?' So asked a frustrated Business Day TV executive. This was, of course, in the context of the 'stolen Tweets' story, one of several copyright stories to make the news recently.

The stolen Tweets story related to the fact that CNBC Africa had copied a number of the Tweets that Business Day had posted in respect of on the mid-term policy speech (the mini-Budget)*. Here's one of them: 'Largest wasteful expenditure is consultant services. Better contract management needed. Proposes stricter control of consultancy fees.' CNBC Africa admitted that it had done wrong and it apologised. It put the blame on a junior intern and it promised that there would be strict disciplinary action.

So do different rules apply to Twitter postings? The answer's no, and we know this from a case that we reported on some time back, one regarding a press photographer called Daniel Morel. In 2010 Morel took a series of dramatic photos of the Haiti earthquake and posted them on Twitter. When a media house used these photos without his permission, Morel sued for copyright infringement. He won his case, with the US court noting that although Twitter's Terms of Service may encourage people to share the pictures they post, it does not deprive them of their copyright. It's not a bad thing to remind ourselves from time to time that the internet has not destroyed copyright – something posted on the internet enjoys copyright in the same way that something that's printed on paper does.

But is a Tweet different from a photo posted on Twitter? In order for any piece of writing to enjoy copyright it must be original, which in copyright terms simply means that it must have been the result of the author's own endeavours and not copied. So the law certainly doesn't require the writing to be creative or clever. Yet there is a sort of de minimis threshold, with the law requiring the writing to have at least a modicum of substance. So, for example, a court held that the song title The Man Who Broke the Bank at Monte Carlo was not substantial enough to enjoy copyright. Many people feel that advertising slogans are in the same category, which is one of the reasons why companies register them as trade marks. Yet in a recent UK case called Meltwater, the court held that newspaper headlines can enjoy copyright because they do often involve skill and effort (when you're finished reading this article go back to the title and you'll see what I mean!) A Tweet, being anything up to 140 characters, is usually longer than a headline. And there's some skill involved in getting a point across in so few characters. So yes, a Tweet will often enjoy copyright. But it does of course depend - if you Tweet something like 'I'm really angry' don't expect legal exclusivity!

The stolen Tweets case has been compared to the on-going case of Moneyweb and Media 24. This is the case where Moneyweb alleges that Media 24 has, through its Fin 24 service, infringed Moneyweb's copyright by simply copying parts of its articles, without bothering to summarise them, and without any attribution or links to the originals. Media 24 claims that what it's done falls within the fair copying defence, and that it's part and parcel of the relatively new service of news aggregation. The Moneyweb case is, in fact, closer to the Ferguson case than the stolen Tweets case.

Sir Alex Ferguson, the recently-retired manager of Manchester United, has recently published a book called My Autobiography' (no copyright in that title!). Given Ferguson's long and successful career, as well as his penchant for plain speaking, the book has created considerable interest. But the BBC managed to annoy Ferguson and his ghost-writer by quoting great chunks of the book. The BBC claimed that this was fair dealing.

So just what is fair dealing? Well we can look to section 12 of our Copyright Act for an answer, and we'll be told that the copyright in a written work will not be infringed by fair dealing which is for the purposes of criticism, review or reporting current events, if the source is mentioned. But just how much is fair? Well here we can look to the words of one of the UK's greatest ever judges, Lord Denning: 'It is impossible to define what is "fair dealing". It must be a question of degree. You must consider first the number and extent of the quotations and extracts. Are they altogether too many and too long to be fair? Then you must consider the use made of them. If they are used as a basis for comment, criticism or review that may be a fair dealing. If they are used to convey the same information as the author, for a rival purpose, that may be unfair. Next you must consider the proportions. To take long extracts and attach short comments may be unfair. But short extracts and long comments may be fair.'

On to our final story. Robin Thicke's mega-successful song Blurred Lines, which he performs with Pharrel Williams, is almost guaranteed to make you feel good. Except perhaps if you're one of the children of the late singer and songwriter Marvin Gaye. Gaye's heirs claim that Blurred Lines infringes the copyright in three of Gaye's songs, particularly the song Got to Give It Up. After allegations of copyright infringement surfaced, Thicke offered the family a settlement which they refused. He then went to court seeking an order declaring that his song doesn't infringe copyright, and the family counterclaimed for copyright infringement. The matter's on-going.

This case raises some interesting issues related to what's sometimes referred to as the 'idea/ expression dichotomy'. What this means is that copyright protects the expression of the idea but not the idea itself. Thicke admits that he was inspired by Marvin Gaye and he's been quoted in the press as follows: 'Pharrell and I were in the studio and I told him that one of my favourite songs of all time was Marvin Gaye's Got to Give It Up. I was like, "Damn, we should make something like that, something with that groove"'. (He may have phrased this slightly differently in his court papers!). But he claims that the similarities between the songs are confined to 'commonplace musical elements', including the high falsetto voice, vocal and musical layering, and beat. He argues that Blurred Lines was intended to be a tribute to an era and reminiscent of a 'sound' or genre, but that there's been no copying. As copying is a requirement for copyright infringement, the case will probably go down to expert evidence.

This case is quite similar to a case we reported on some time back, the case of Guy Hobbs and Elton John. What happened there was that Hobbs claimed that he had penned a song called Natasha, which was based on a short relationship he had with a Ukrainian woman whilst he was working on a Cold War-era Soviet ship. He claimed that he had sent his song to Elton John but that it had never been acknowledged. He claimed that Elton John's song Nikita was an infringement of his copyright. A US court found against him, saying that the shared features - the theme of Cold War love, the concept of unanswered correspondence, the use of generic phrases, and the repetition of the song title in the chorus – were too common and clichéd to enjoy protection.

All in all, an interesting few weeks for copyright!

*See our story on Twitter's IPO to see whether or not Tweet is a trade mark.

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