RGBDS is an assembler/linker package that produces Game Boy programs.
rgbds-linux is a fork that aims to act more like a traditional POSIX application.
Releases, including Unix source tarballs and Windows executables, are hosted on Github. You can also download the latest source directly with git:
git clone https://github.com/bentley/rgbds/
Vim syntax highlighting file. Put it in ~/.vim/syntax