Homegear is described as 'currentely supports the following systems:'. There are six alternatives to Homegear for a variety of platforms, including Mac, Linux, Windows, Self-Hosted solutions and Android. The best alternative is openHAB, which is both free and Open Source. Other great apps like Homegear are Homebridge (Free, Open Source), FHEM (Free, Open Source), EVA ICS (Free, Open Source) and IP-Symcon (Paid).
Homebridge is a lightweight NodeJS server you can run on your network that emulates the iOS HomeKit API. It supports Plugins,community-contributed modules, that provide a basic bridge from HomeKit to various 3rd-party APIs of "smart home" devices.
FHEM (TM) is a GPL'd perl server for house automation. It is used to automate some common tasks in the household like switching lamps / shutters / heating / etc. and to log events like temperature / humidity / power consumption.
EVA ICS is a platform for automated control and monitoring systems development, for any needs, from home/office to industrial setups. It is completely free for non-commercial use as well as for commercial, on condition that enterprise integrates it on its own.