Specialist software to format the likes of a screenplay or theatre script has for a long time been the kind of luxury few can afford. Granted, there are some cut-down, low cost packages available, but movie industry-standard tools such as Final Draft cost over £130, and story-plotting software such as Dramatica doesn't come cheap either.

Celtx does. Because this is a testament to the growing maturity of the open source software movement, where it's producing sophisticated tools to tackle even niche areas of computing. Celtx has been around for a couple of years now, and its latest iteration, version 0.9.9.7, proves to be a sophisticated and welcome tool. And, crucially, it's free of charge.

It's an application with several tricks up its sleeve. You start at a project templates menu, where from the left pane you can pick between film, theatre, audio-visual, audio play, storyboard or text projects, and in the right-hand pane are some sample projects to take a look at. It's worth doing that, to get a feel for how the program does its business, and you can also download further sample projects should you so wish.

What you'll quickly get an idea of is just how complete - if a little raw - a tool this is. Dig into the project of The Wonderful Wizard Of Oz, for instance, and a project library pops up on the left-hand side. So click on the screenplay and up pops the script, but as you move down the list, there are options for everything from a shooting schedule through to location photos. Many of these choices are take it or leave it, and the exhaustive nature of what's provided can be a little overwhelming, but this really is some piece of work.

And crucially, it does the key jobs well. Learning script formatting, a necessary evil for getting your foot through the door at most production companies, can be a devil of a job, yet Celtx makes it a breeze. The biggest compliment it's perhaps possible to pay is that it's as seamless as any of the more expensive tools that have dominated the industry for a good decade, and opens up a seemingly dark art to an audience of people who simply couldn't afford to join in before.

Celtx, after we'd navigated the learning curve, caused us few problems, especially once we got into the habit of taking or leaving the parts we wanted to use or otherwise. It's an ambitious tool that in one swoop has removed the need for the enthusiastic amateur scriptwriter to fork out an entry fee to be able to stand much chance of getting into what is, after all, a tough business to crack. Now? You just need to add writing talent.

That's, ahem, where this reviewer may have come a bit of a cropper...

This is an invaluable piece of software for the scriptwriter, and one that shows open source at its best; competing well against commercial software on its own turf.