While you might be tempted to think that I am going to write more about anger, I think that a more appropriate term would be passion. FreeSwitch was created for the same reasons that so many other open-source projects happen; a passion for a particular problem space that was not going to be addressed any other way.
Part of FreeSwitch’s methodology has been to embrace existing technologies as much as possible. Often, existing libraries are integrated into the product, rather than new modules being written. FreeSwitch can do this because it is written under the Mozilla Public License (MPL), and thus enjoys more freedom than GPL stuff does (with apologies to Richard Stallman ;-)
FreeSwitch is a fairly new open-source telecom application. While this means that it is arguably not as mature as something like Asterisk, it also means that it can incorporate newer ways of thinking about software development, and benefit from lessons learned along the way. Many of the FreeSwitch team earned their stripes with the Asterisk project.
FreeSwitch is something to keep your eyes on.