The latest stable is UnrealIRCd 5. More information on current and future UnrealIRCd 4 releases can be found at https://www.unrealircd.org/docs/FAQ#What_is_the_current_version_and_when_will_next_version_be_released.3F
There is also oldstable, UnrealIRCd 4, which will be supported until December 31, 2020. This gives users 12 months to upgrade from 4.x to 5.x.
IMPORTANT: The old UnrealIRCd 3.2.x series are no longer supported. The End Of Life announcement was in December 2015 and as of January 1 2017 all support for 3.2.x has been stopped, including security fixes. See https://www.unrealircd.org/docs/UnrealIRCd_3.2.x_deprecated
We really appreciate it when you report bugs and feature suggestions here, this helps us to fix issues and move UnrealIRCd forward. If you are in need of support, however, then please use the forums https://forums.unrealircd.org/ or IRC Support channel ircs://irc.unrealircd.org:6697/unreal-support instead. Also don't forget to check out our excellent support resources: