iBus is described as 'Intelligent Input Bus. Input Method for many languages especially CJK (Chinese, Japanese, Korean) but not only' and is an app. There are three alternatives to iBus for Linux, BSD and Mac. The best iBus alternative is UIM, which is both free and Open Source. Other great apps like iBus are fcitx and scim.
Uim is a multilingual input method library, whose goal is to be a flexible development platform and useful user environment for input methods of all languages.
UIM is the most popular Mac & Linux alternative to iBus.
UIM is the most popular Open Source & free alternative to iBus.
Fcitx ['fa?t?ks] is a input method framework with extension support. Currently it supports linux and Unix system, like freebsd. It has three builtin Input Method Engine, Pinyin, QuWei and Table-based input methods.
The Smart Common Input Method (SCIM) platform project provides not only a user friendly, full featured input method user interface for POSIX-style operating systems (including Linux, FreeBSD and other Unix), but also a development platform to make input method development easier.
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