Kitserver: a Lua module for Sider 6 and PES 2020
If you are old enough, you may remember that the very first Kitserver (for PES 3) was a small program that allowed the game to load alternative kits (3rd, 4th, European, etc.). It was initially released in 2003. Over the next few years, Kitserver had grown into a more generic tool - very similar to what sider is now, but the original name stuck to it.