Japanese developer
Kazuho Oku offered a tool to use custom scripts in Google Chrome.
So far (the current version is 0.1)
Greasemetal may be of interest only to advanced users, since it does not contain a UI for managing scripts (you must manually copy the necessary scripts into the appropriate folder).
Greasemonkey functions are also not supported, so it is recommended to use scripts that work not only in FF, but also in Opera, and in Safari.