StartOS (formerly Ylmf OS) is a Chinese Linux distribution. StartOS is an operating system which is free and open-source software. In the beginning it was based on Ubuntu., but starting from version 4.0 it adopted custom package management (called YPK) and system installer, though the underlying live medium is still built using Ubuntu's Casper tool. Its user interface closely resembles that of MicrosoftWindows XP. The distribution was originally not available in the English language, though shortly after the initial release in late 2009 an English-language version of Ylmf OS was released.
Despite the very similar likeness to Windows XP's Luna theme—the default theme for Windows XP—Microsoft does not appear to be planning to take any sort of action against the operating system or its developers.