I'm going to keep this short, and simple. I've got logs - I've tried this with your FML installer code, and my modified version (see my github/pull to your repo).
Every time I try to set up a Forge MCP workspace (IE forge downloads all needed resources, patches them), I run in to errors when patching the minecraft source. This is the correct MCP version, the correct MC Jar version, and the correct Forge version. Nothing is wrong in the downloads/resources department. These files (MC jar, etc..) have in no way been altered prior to their being processed by MCP and Forge.
After Forge fails to automate decompilation, I try to decompile - I am told consistently (IE every try) the a certain class `qp' is missing.
My diagnosis: It looks like the wrong patchfiles got included. I may be wrong, however. Regardless, decompiling consistently fails.
Links (Be sure to read any #'d comments):
`forge_i_c.log' (Console session, /bin/bash): http://pastie.org/6575782 (PB captchas are currently broken, only got to post one time)
`forge_i.log' (Forge install, referenced from console session log): http://pastebin.com/NWFxvfXC
My pull request with the patch I applied (this works - nothing is wrong here): https://github.com/MinecraftForge/FML/pull/202