FontForge

An outline font editor that lets you create your own OpenType, TrueType, CID-keyed, multi-master fonts and more... or simply edit existing ones.

Web site at fontforge.org

Building from source

Instructions are listed in INSTALL-git.md, you can also find a list of dependencies in .travis.yml.
Fontforge supports Python >= 2.6, but the testsuite is solely Python 3-compatible.

Also check out the developer documentation.

Contributing guidelines

Please see CONTRIBUTING.md.