HylaFAX™ is an enterprise-class open-source system for sending and receiving facsimiles. This is the place where users can find HylaFAX+ support, work, and releases. The "+" means that it is better.
IAXmodem is a software modem written in C that uses an IAX channel (commonly provided by an Asterisk PBX system) instead of a traditional phone line and uses a DSP library instead of DSP hardware chipsets.