DaemonUmbra

I accomplished this through the use of a "generated" Gradle sourceset, then including that sourceSet in my run configurations (in runs -> mods -> <my mod name> under sourceSets.main) To have this sourceset included in your built jar requires extra configuration to the jar task, adding from sourceSets.generated.output to it. (This is all Gradle configuration, if you have further questions please try reading the Gradle Documentation)

I still don't understand why people think "I MUST REMOVE ALL TRACES OF FORGE", the only legitimate reason to uninstall Forge is if it's corrupted and needs to be reinstalled. Why would someone delete their launcher when uninstalling Forge is literally as simple as deleting a few files?

I find that to be factually false. Please do tell where you are getting your info from.

Please read the Logs section of my signature below and provide the appropriate log in the appropriate manner.

What do you mean "Mods Button"? Are you expecting a button in the launcher that will take you to the mods folder?

Remove Optifine

I won't know unless it crashes again and you send me another log

This is on Optifine, and they do have a version that is compatible with at least one version of Forge, however it is a preview version and the only one of its kind at the moment. Edit: and even then it's only designed to be compatible with one version of Forge, a version that is now obsolete.

Darkhax, I thought you knew better than this... Enchantment Descriptions is broken and/or poorly made and won't run on a server

Please provide the debug.log from the server's logs folder

What launcher are you using? Please provide a screenshot.

Sounds like your Java installation went wrong

Provide a debug.log for the run with Java 8

You need to use Java 8, 9, or 10 with Forge. To support 11 Forge would need to drop support for 8 (due to a core library doing so) which can't be done because 8 is what Mojang ships with the game.

The installer works for every system, a crash at runtime does not necessarily mean the installation went wrong. Please provide the debug.log from the server's logs folder

Ok, and you went for universal instead of installer, why?

I'm always suspicious when people say "The official site" or something like that, because often they have been fooled by a pretender. Please provide a URL

Did you run genEclipseRuns? Actually that may have been moved into the eclipse task

Where are you getting Forge from and how are you trying to install it?

Sounds like you either do not have Java installed or something went wrong and Java is no longer associated with the .jar file extension

So my first question is why are you putting an installer of any kind in your mods folder

What are you confused about?

1.7.10 is no longer supported on this forum due to its age. Please update to a modern version of Minecraft to receive support.

Please refer to my signature below for info

Please keep this forum in English. That's not even a Forge crash, that looks like Vanilla's installation somehow got fouled.