Call out the chaperons — they’re practically touching! Apache and Microsoft IIS market share! They’ve almost met in the middle at 50%! Six inch space and no kissing, please!

Well, close, but not quite. Apache continued its “winning streak” in September over Microsoft’s Internet Information Server, but by a smaller margin than the month before (when Netcraft, which watches these kinds of things like a hawk, said that IIS was poised to challenge Apache’s market share lead sometime soon).

Part of this — as we’ve reported before — is due to Tomcat and to Google’s big server switch in 2006. Both of these phenomenons had a profound affect on Apache’s numbers, but were not in and of themselves an indicator of any slippage.

However, all that said, IIS is growing thanks to a rise in social networking sites like MySpace and Windows Live Spaces, both of which use ISS.

Says Netcraft:

The high growth so far this year has been largely driven by the increasing number of online blogging and social networking communities. This month sees strong growth in the number of sites at Windows Live Spaces, MySpace, and Blogger appearing in the survey. The increased popularity of these blog hosting services continues to have a dramatic effect on the web server market shares: Apache suffered a sudden decline in share when sites at Blogger switched to Google’s GFE.

Apache gains over 3 million hostnames, and around 0.9 million active sites this month. But this is not enough to prevent its market share declining closer to the 50% mark, as Microsoft also gained over 3 million hostnames (a large part of which come from MySpace and Live Spaces, both of which use its Internet Information Server).

So the battle continues.

The executive summary for Netcraft’s latest Web server market share report says it all: “Microsoft’s recent gains raise the prospect that Windows may soon challenge Apache’s leadership position.”

Or does it?

The August Netcraft report, out on Monday, showed that the trends established over the past year concerning Apache Web server and Microsoft IIS have continued unabated. We reported on the trend last month in our article, Apache loses more ground in latest Netcraft report, and we found that things are not what they first seemed. Yes, Microsoft IIS is seeing an uptick, but the Apache decline is not entirely a result of that growth.

Mark Brewer, CEO of Covalent Technologies, an Apache support provider based in Walnut Creek, Calif., spoke with us for that article, and his analysis then still applies to the August report. Part of the decline can be blamed on Apache Tomcat, a Web container developed by the Apache Software Foundation, which also created the Apache Web server. According to Forrester Research Inc., 51% of enterprise-class production-level deployments run Tomcat. So, simple deduction: As Apache Tomcat increases, Apache Web server decreases.

“When doing a Netcraft lookup on Web sites that are known to be using Tomcat, [the search] frequently does not report as Apache,” Brewer told us during a visit to our offices in Needham, Mass. Examples include the JBoss site, the Sakai site and Wal-Mart Stores Inc.’s digital photo center Web site.

Additionally, Brewer said most Web sites that use Tomcat to serve up Web content via HTTP would show up in surveys as a “mod_jl.conf” entry — not Apache — and thus would not be counted as sites that use Apache servers.

Google’s “to blame” too. Netcraft originally classified Google servers as Apache machines, but earlier this year the firm began reclassifying these servers in their own unique category. The move affected Apache market share

But this isn’t the whole story. Even as Tomcat/Google cannibalizes Apache, IIS is seeing gains. Netcraft’s report says, “It’s worth noting that Apache has lost market share to another open source server, lighttpd (1.2% of all sites), and Google (4.4%) as well as Windows. But if Microsoft continues to gain share at its current pace, it could close the gap on Apache sometime in 2008.”

That’s a key point, because 2008 is when the new Microsoft Server is *supposed* to come out. We’ll be watching.