Okay, I can understand that.
But it seems that does not support older versions of Minecraft, like 1.5.2.
My use-case is that I would like to create extra mods for a mod package that me and my friends are using.
I guess that this might be a slim use-case for trying to convince you that it might be good to support even older versions. But I am guessing that there might be others trying to do the same thing as me.
So my new suggestion being that you could add a small documentation on your site, on "How to do stuffs for the 1.5.2".
Might not be a really bad idea, as people would much rather it actually works directly than having to change stuff. But if they are determined on getting it to work for 1.5.2, I guess they'd like a little guidance before having to go through the trouble I went through.
If you want, I can write a documentation page for this. I'm more than happy to contribute stuff. ( Documentations, development tools, environmental tools, source code )