XChat was once the most popular of the X11 clients, but by 2016 has fallen into abandonment - the last meaningful releases were inMay 2010, the user forums have been taken offline, and some distributions have begun to remove it from their repositories as unmaintained software. In it’s present state, we can no longer recommend XChat.
Hexchat is a fork of XChat that is activelymaintained, with a substantial following. For all intents and purposes, it’sthe spiritual successor to XChat, and for most users, likely to be an easyreplacement.
At the height of its popularity, XChat was widely included in Linux distributions,and had an official Windows port that was gaining ground rapidly on mIRC. It wasthe Windows port and decisions around it by XChat’s maintainer that would provefatal. XChat was released under the GPL license, a copyleft free software license.The maintainer unilaterally declared that the official releases of XChat wouldbe shareware under Windows, citing the rising popularity, complexity of development,and cost of maintaining development tools for Windows. The backlash from this ledto a number of unofficial ports, the loss of virtually all outside developers,and most importantly, the loss of the community’s trust - even among Linux/Unix userswho were not directly affected by the change.
One of those unofficial Windows ports,HexChat,grew up into a not just a port, but a viable, active, and well-maintained fork ofXChat, and the community of users and developers have largely followed.