Any Soft Keyboard is an open-source, on-screen keyboard with multiple languages support with emphasis on privacy.
This is one of the most customizable keyboards available.

To activate: Launch 'AnySoftKeyboard Settings' App, and follow the instructions.

Main features:

Multi languages keyboard support via external packages.
Completion dictionaries for multiple languages.
Also completes your typed words from you contacts names (Android 2.0+)!
And, learns your typing behavior to provide next-word prediction.
Multi-Touch support (as in, pressing SHIFT along with other characters).
Extension keyboard (swipe your finger all the way up out of the keyboard).
Voice Input support (Android 2.2+).
Compact/Phablet Mode.
Gesture support:
** Experimental Gesture-Typing (enable in the Settings app).
** Swipe left or right to switch layouts.
** Swipe up to shift.
** Swipe down to close the keyboard.
Theme support (comes with a few built-in skins, and more available in Play Store).
Night Mode: Quiet, Dark keyboard at night time (enable in the Settings app).
Power-Saving Mode: No vibrations, sound, suggestions and a dark theme (enable in the Settings app).
Build-in user dictionary words editor.
Build-in abbreviations dictionary: create shortcuts for words and sentences.
Utility keyboard (swipe up from space-bar):
** Clipboard actions copy, paste, select-all, select selectively (long-press select and use arrow keys).
** Voice input
** Arrows
And many more features!

Support at: https://github.com/AnySoftKeyboard