I don't know whether you've helped contribute to J D Salinger's legal fund, but I know I have, having purchased at least one, and possibly two copies of The Catcher in the Rye in the last few years (it's a bit of a fixture on school reading lists). I've done my small bit, in other words, to keep sales of this classic of teenage angst ticking over at around 250,000 a year – an impressive figure given that its accumulated sales are said to be something like 65 million copies. And without that fact I don't think we'd have been reading about the latest Salinger lawsuit, brought against a mysterious Swedish writer, J D California, who has produced a sequel he calls 60 Years Later: Coming Through the Rye.

A taste for litigation as frequently indulged as Salinger's requires two things. You have to be bothered and you have to have the funds. Salinger manifestly scores on both counts and so there have been a string of court cases – stopping biographies here and blocking film adaptations there. In the current suit, Salinger's lawyers argue that he retains exclusive rights to the character Holden Caulfield and somewhat redundantly add that their client is "fiercely protective of his intellectual property". You don't say.

He isn't unique in that of course. Lots of writers and artists take a dim view of unlicensed exploitation of their work – and the richer ones will generally police any attempt to cash in on work they've done themselves. J K Rowling could spend a long evening comparing judicial rulings with Salinger and they'd probably still have a lot of stuff to talk over at breakfast the next day. What is slightly unusual about Salinger, though, is that he has no interest in cashing in on his work himself – and apparently sees no virtue in allowing his creation off the leash into the larger culture. He hasn't sued in the past because he wants artistic control over who's cast to play Holden Caulfield, or over what percentage of the resulting profits should go into his bank account. He's sued because he doesn't want Holden to have any life independent of the novel. He is, in rather literal form, asserting his authority over what he created.

What's intriguing about this is how old-fashioned it is, and how stubbornly it resists the prevailing cultural tide of the last sixty years. It's jamming the door against meta-textuality, mash-ups and imaginative after-life – a culture in which it is understood that any really significant creation evolves towards a shared ownership, between creator and audience. There are good reasons for the maintenance of the legal fiction that Holden Caulfield is Salinger's alone to dispose of. But that legal fiction doesn't register the reality, which is that my Holden and your Holden are very different things, and that mine or yours might have a continuing life that Salinger can do nothing about. And Salinger is surely on even shakier ground in trying to prevent himself from becoming a character in other people's creations – preventing the publication of a fictional "interview" with him and objecting to his imagined presence in J D California's book. If he wanted to avoid mythology, he should have given a few more interviews.

Had Jane Eyre still been in copyright when Jean Rhys published Wide Sargasso Sea, Charlotte Brontë could presumably have prevented publication. But would readers have really wanted her to? And would cinema-goers have been happy if the Bogart estate had prevented Woody Allen from drawing on Bogie's film image in Play it Again Sam? There comes a point when people – both real and imaginary – step beyond their origins to become something else and that section of the world should be as accessible to writers as the concrete world of facts. I don't think that Salinger is really protecting the products of his own imagination with this lawsuit. I think he's trying to limit the freedom of someone else's.

Big train a-comin'

Later this year London's Serpentine will host the first Jeff Koons show in a British public gallery – and one can only hope it doesn't cost them anything like as much as the Koons under construction for the LA County Museum of Art. Koons proposes to hang a full-sized replica of a 1940s locomotive – with rotating wheels and smoking stack – from a crane. The museum has reportedly already spent $1.75m on feasibility studies and the total price is estimated to be north of $25m. The first thing I thought of when I saw it was George Wylie's The Straw Locomotive, in which the Glasgow-based artist hung a lifesize straw locomotive from the giant Finnieston Crane. Koons's piece is sufficiently different, I'd have thought, to make it very unlikely he'll add to his list of appearances in copyright infringement suits. But it's also sufficiently similar to make you wonder if he passed through Glasgow in 1987 and a seed of inspiration was sown.

Coming out of Aunt Dan and Lemon at the Royal Court recently I found myself wondering whether there are sometimes grounds for a theatrical refit – the equivalent of a liner being taken into dry-dock and given a more efficient set of boilers. The prompt here was the part Henry Kissinger plays in the drama, as the subject of an eloquent and passionate defence by the Aunt Dan of the title. In 1985 Kissinger's status as a liberal bogeyman was pretty much unchallenged, but one wonders whether he resonates in quite the same way for younger audiences now. I'm guessing that the youngest in the audience could really do with a surtitle footnote (or headnote) sketching in details of the secret bombing of Cambodia and the support for Latin American dictators. And even for audiences who remember him as a poster boy for ruthless realpolitik there's a difference between historical memories and the immediate jolt of provocation that Aunt Dan's speech delivered back then. The knee doesn't jerk in quite the same way. If the play is to extend its active service life for another 30-odd years it's time surely for the Kissinger power-unit to be unbolted and a gleaming Donald Rumsfeld put in its place.