beat is the canonical tool for working with the following file format specifications:
beat v03 (Windows binary and source code)
Note: currently, beat v03 uses a quadratic function for creating delta-based BPS patches. This can be quite slow, especially on files over 32MB in size. As such, for the time being I'd strongly recommend using Floating IPS by Alcaro instead. You can download it here.
beat is licensed under the GNU GPLv3.