There are three major issues in using or re-using open-source software; quality, documentation, and licensing terms. We've seen above that if you exercise a little judgment in picking through your alternatives, you will generally find one or more of quite respectable quality.

Documentation is often a more serious issue. Many high-quality open-source packages are less useful than they technically ought to be because they are poorly documentated. Unix tradition encourages a rather hieratic style of documentation, one which (while it may technically capture all of a package's features) assumes that the reader is intimately familiar with the application domain and reading very carefully. There are good reasons for this, which we'll discuss in Chapter 18, but the style can present a bit of a barrier. Fortunately, extracting value from it is a learnable skill.

It is worth doing a Web search for phrases including the software package, or topic keywords, and the string “HOWTO” or “FAQ”. These queries will often turn up documentation more useful to novices than the man page.

The most serious issue in reusing open-source software (especially in any kind of commercial product) is understanding what obligations, if any, the package's license puts upon you. In the next two sections we'll discuss this issue in detail.