Linux has always been better received in the server market than the desktop market, where it's compatibility with UNIX and POSIX-compliance has made it a great fit for companies who aren't about to shell out for UNIX licensing. The past year along has seen significant Linux server growth, which now accounts for over 13% of the market.
They share this with many top players, including Microsoft, who has more than a third of the total market. While UNIX-like operating systems still make up the lion's share of all servers active in the world, vendors who support and sell Linux will likely have to find new ways to erode Microsoft market share rather than others, or they risk stalling growth.
IBM remains the number one vendor for selling servers, selling significantly more than HP, Sun, Dell and others.