Most people like the idea of open source software. For many, the problem is the execution.

Everything about open source seems to be written by geeks for geeks. The usual marketing sheen of traditional commercial software is absent. That's a mixed blessing: It is refreshing or leads to a muddle of strange, acronym-laced verbiage.

VirtualHosting.com provides some help with a look at what it considers to be the top 50 open source VoIP applications. The categories are Session Initiation Protocol (SIP) proxies; SIP clients; H.323 clients; inter-Asterisk (IAX) clients; Private Branch Exchange and interactive voice response platforms, stacks, and libraries; developers; and miscellaneous. The editors provide brief definitions of each category.

Garrett Smith, a VoIP equipment, software and services executive, says on his blog that VoIP systems are selling like cyber hot cakes. While he doesn't distinguish between open source and proprietary products, it's clear that a good deal of what is selling is the former. A year ago, he says, one or two VoIP deals of 200-plus seats would be made per week. In a two-day span in mid-February this year, Smith said that he saw three 200-plus seat contracts, "a handful" of 50- to 75-seat deals, and deal of more than 4,000 seats in 26 locations. In addition, margins are better and deals are easier to close. He offers three reasons this may be happening: the technology is better trusted, businesses are better educated and sales people are doing their jobs better.

Call centers increasingly use an open source VoIP approach. VoIP News describes how three vendors have customized the popular Asterisk PBX for use in this setting. The piece says Fonality's PBXtra Cell Center Edition is aimed at 2- to 200-seat settings. asterCRM is compatible with all Asterisk-based VoIP systems including, the piece says, pure Asterisk, Magiclink IP PBX and Trixbox. Vicidial, the writer says, is a complete inbound/outbound call center software suite. All three systems, the writer concludes, are adequately supported by software developers.

Open source VoIP is a difficult area to describe simply because it is filled with so many little-known companies. That isn't always the case, however. In some instances -- such as this announcement from earlier this year -- at least one of the firms involved is well known. In January, Broadcom and Trolltech announced a partnership to develop a complete multimedia-enabled VoIP platform for phone makers. The product will combine Broadcom's VoIP technology with Trolltech's soon-to-be-released Qtopia software. The release, which has the complicated details, says Qtopia is a software application platform and user interface for Linux devices that is being designed to work with Broadcom's BCM1103 and BCM1180 multimedia co-processor.

The open source Mozilla Firefox browser, which has captured a healthy piece of the browser market from Microsoft's Internet Explorer, comes with an e-mail service extension called Thunderbird. This week, Mozilla announced that it is evolving to become Mozilla Messaging and will incorporate Thunderbird 3. ZDNet's Russell Shaw picked out a piece of a rather lengthy post on the move by Mozilla Messaging's CEO-designate David Asher to speculate that VoIP integration -- making voice part of Mozilla Messaging and, therefore, part of a future version of Firefox -- is likely.