FML and Forge FAQ - MinecraftForge/FML GitHub Wiki

The relationship between FML and MinecraftForge

FML was conceived to address the need for Minecraft Forge to have a reliable mod loading component on the server. However it is and will remain independent of Minecraft Forge.

FML has since taken over all modloading responsibility for Minecraft Forge, since about mid 1.2.5, including the client.

Minecraft Forge ships with a recent version of FML. Generally new versions of FML are submitted as pull requests to Minecraft Forge as needed, or occasionally to bundle up minor fixes.

You can always find out the version of FML included by examining the README-fml.txt file that ships with FML and Minecraft Forge- it contains the build information.