Your articles on configuring the pppd are outstanding [see Tony Mobily's “Configuring pppd in Linux” parts I and II in the February and March 2002 issues of LJ]. This is the way a HOWTO should be done—excellent hands-on information that works, with complete directions for us beginners. Well done! You can ask Tony back any time.

—Jack Dennon

I read with interest Larry Rosen's “Unbiased License FUD” in your March 2002 issue. I am appreciative that Larry is dispelling the confusion about how the GNU GPL works. He is quite correct that to have obligations under the terms of the GNU GPL, one must actually create and/or distribute a derivate work of some copyrighted software licensed under the GNU GPL.

However, while dispelling FUD in that area, Larry (perhaps unintentionally) helped to spread similar FUD himself. In his article, Larry propagated the idea that the “GPL is an infection”. Infections are (according to “dict” on my Debian GNU/Linux system) things “which taint or corrupt morally” or “cause...disease”.

This sort of fear mongering about the GNU GPL became all too common during summer 2001, when various high-ranking executives of Microsoft called the GNU GPL an un-American cancerous virus that ate up software like a Pac-Man. I doubt that Larry or your magazine want to affiliate themselves with that concerted campaign of FUD.

As a strong advocate of software freedom, I often tell people: “The GNU GPL is not a virus; by contrast, it vaccinates you from harm.” The GNU GPL is designed to share freedom with all who benefit from the software. No one is required to “join the club”, but when you do choose to create derivative works of GNU GPLed software, you have obligations to the community. The GNU GPL is designed to create a software commons, with provisions that help avoid the tragedy of the commons.

I urge your editorial staff and Larry himself to avoid using biased terms like “infection” when trying to give “Unbiased License” information. The unbiased way to describe the GNU GPL's nature in this regard is simple: “The GNU GPL requires that those who distribute derivate works license the source of the derivate work in a GPL-compatible way.”

—Bradley M. KuhnVice President, Free Software Foundation

Larry replies: Bradley, thanks for your letter. I usually try to avoid the term “infection” when speaking of the GPL. However, I used that word in that particular article because, as I quoted directly in my second paragraph, the reader who responded to me used that word. I certainly did not intend to propagate the notion that the GPL has virus-like attributes, in the sense of things “which taint or corrupt morally” or “cause...disease”. I perhaps should have used the word “inheritance” instead, as I have done in my other writings about the GPL, because that word has more positive implications. Indeed, I have recently started to use the term “reciprocity” to describe the effect of the GPL and similar open-source licenses (including the MPL and CPL). Those licenses require licensees to reciprocate by licensing their derivative works under the same license as the work they were given. In contract law terms, I contend, the reciprocity obligation is the “consideration” you pay for the grant to you of the free license to the original code.

I have a few comments regarding David Bandel's Focus on Software column in the March 2002 issue of Linux Journal. First, great job, David. Keep up the good work! For me, your article is second only to Freshmeat when it comes to discovering new software. Second, I was thrilled to see coverage of Vipul's Razor (razor.sourceforge.net). I've found it to be incredibly effective in weeding out my daily dose of spam.

Although I am a long time Procmail user, I've often found its recipes difficult (at best) and cryptic (at worst). I can't begin to count the hours I've spent writing and debugging what should be a fairly simple filter. I think many of even the more hard-core Procmailers would be pressed to disagree with me on this point.

So, it was with no small amount of giddiness that I discovered Mail::SpamAssassin. This module (accessible via CPAN.org) is a plugin to the Mail::Audit module. The true advantage is that, because it's Perl, you can easily filter your e-mail through a Perl script. I have a tutorial covering this at PerlMonks (www.perlmonks.org) under the Tutorials section entitled (appropriately enough) “A Beginner's Guide to Using Mail::Audit and Mail::SpamAssassin”. Using these modules gives you the power of Perl (renowned for its ability to parse text) to filter your e-mail. I've been using this for several months now, and I've found that approximately 99% of my daily spam is filtered appropriately. And, I'm proud to report that none of my e-mail has been lost. Again, you're doing a great job. Keep it up!

—Stephen E. Hargrove

Seymour Cray didn't like virtual memory and has been quoted as saying: “Memory is like sex; it's better when it's real.” Whereas Paul Barry (LJ March 2002, Letters) apparently wasn't aware of Seymour's quip, Linus certainly was; his comment comparing software to sex is an obvious allusion. Perhaps it's not that Linus needs to choose his words more carefully; perhaps it's that authors should explain the literary significance of these words for the younger generation.

—Collin Park

After spending a few nights with LJ [see David Bandel's “Taming the Wild Netfilter” in the September 2001 issue, available at /article/4815] at hand's reach to configure my firewall, I came across the URL www.boingworld.com/workshops/linux/iptables-tutorial. This is to me the best source I have found on Netfilter. I believe the reference to Rusty Russel's document is a tribute to Rusty's own work, but the document is not usable for a basic user like me, a simple, average Linux user! Please to advertise this URL to your user if they have troubles using the wild, wild Netfilter.

—Thomas Smets

For more on Netfilter, see David Bandel's more advanced article “Netfilter 2: in the POM of Your Hands” in this issue.

—Editor

Gary Bickford's letter in the February 2002 issue of LJ states: “GTO is an acronym (Gran Turisimo Omologato), which according to AltaVista means 'great accredited tourism', which I suspect doesn't express the flavor of the phrase.”

He's right—Gran Turisimo refers to a racing class (Grand Touring, or GT) of cars, and Omologato (“homologated” in English) refers to the particular group of cars that was built specifically to fulfill the racing organization's requirements. As it turns out, Ferrari cheated on this; they never actually built the number of cars they were supposed to, but the organization never called them on it.

Most Pontiac dealers, when asked where the GTO moniker came from, were at a loss to explain any of this when the acronym was tacked onto the 389-engined version of the Pontiac Tempest.

—David Spellman

I found a small problem when using the caching PHP file [see Bruno Pedro's “Improving the Speed of Web Scripts” in the March 2002 issue of LJ]. The md5 hash is generated by using the PHP_SELF name of the called PHP script. But what if I generate content depending on the query string? I changed from PHP_SELF to REQUEST_URI, so it generates a unique cache file per unique parameters. This way I saved 90% execution time compared to running against my MySQL data sources.

—Kai Kretschmann

In the March 2002 issue, on page 94, “'Using Mix-ins with Python', Linux Journal, April 2000” should read “'Using Mix-ins with Python', Linux Journal, April 2001”, i.e., the referenced article appeared in the April 2001 issue, not 2000.

—Chuck Esterbrook