10. Ghostscript.

Ghostscript is an incredibly significant program for free software-driven printing. Most printing software under Unix generates PostScript, which is typically a $100 option on a printer. Ghostscript, however, is free, and will generate the language of your printer from PostScript.

Ghostscript is available in several forms. The commercial version of Ghostscript, called Aladdin Ghostscript, may be used freely for personal use but may not be distributed by commercial entities. It is generally a year or so ahead of the free Ghostscript; at the moment, for example, it supports many color inkjets that the older Ghostscripts do not and has rather better PDF support.

The main free version of Ghostscript is GNU Ghostscript, and is simply an aged version of Aladdin ghostscript. This somewhat awkward arrangement has allowed Aladdin to be a totally self-funded free software project; the leading edge versions are done by L Peter and a few employees, and are licensed to hardware and software vendors for use in commercial products. Unfortunately, while this scheme has provided for L Peter's continued work on Ghostscript for years, it has also inhibited the participation of the wider free software community. Driver authors, in particular, find the arrangement poor. L Peter's retirement plans mandate a larger community involvement in the project, so he is considering license changes, and has established a SourceForge project.

The third version of Ghostscript is ESP Ghostscript, maintained by Easy Software Products (authors of CUPS) under contract from Epson. ESP Ghostscript is a combination of the gimp-print driver project's drivers and GNU Ghostscript, plus assorted usability patches. This version is not yet in full swing, but it will be available soon, and will hopefully simplify life for owners of Gimp-print-driven printers.

Whatever you do with gs , be very sure to run it with the option for disabling file access (-dSAFER). PostScript is a fully functional language, and a bad PostScript program could give you quite a headache.

Speaking of PDF, Adobe's Portable Document Format (at least through 1.3) is actually little more than organized PostScript in a compressed file. Ghostscript can handle PDF input just as it does PostScript. So you can be the first on your block with a PDF-capable printer.