The source code to VVVVVV! http://thelettervsixtim.es/
This is the source code to VVVVVV, version 2.0+. For more context about this release, see the announcement on Terry's blog!
VVVVVV's source code is made available under a custom license. See LICENSE.md for more details.
In general, if you're interested in creating something that falls outside the license terms, get in touch with Terry and we'll talk about it!
There are two versions of the VVVVVV source code available - the desktop version (based on the C++ port, and currently live on Steam), and the mobile version (based on a fork of the original flash source code, and currently live on iOS and Android).