This sounds like a really silly and unfounded accusation. Do you have any reasoning why railcraft's author would do this?
Well, for one, CovertJaguar really really likes the idea of DRM in mods. Primarily in, duh, Railcraft - he introduced a DRM kind of thing that other people eventually patched out. CovertJaguar, SirSengir, and GregoriousT are the kind of people who would do such a thing where if you install their mod alongside a mod they personally dislike, their mod proceeds to fuck with your game. Why do I say this? Because they're done things like that before:
- CovertJaguar implemented DRM inside Railcraft that would check other mods to see if they'd been modified by other mods and promptly crash your game if so. That is: Railcraft would check, say, RedPower2 to see if it had been modified by a fan-made patch for a bug Eloraam hadn't fixed, and then crash the game.
- SirSengir implemented a function inside Forestry that would query what directory it was inside, and if it was inside the directories used by the Technic Launcher, the mod would proceed to spawn bees that destroyed your world. He did this because the Technic Pack at the time had included Forestry without asking him, and he didn't even bother to ask for it to be removed, just decided "Fuck the user!".
- GregoriousT has had, for a long time, code inside GregTech to crash your game if it is inside directories used by the Technic Launcher - which has necessitated either third-party patching or putting the modpack somewhere else in your filesystem. He's also added code to generally humiliate other modders, as well as deliberately creating incompatibilities with other mods and then blaming the other mod.
If that's true, then that's just plainly being a jerk.
However it's understandable if he/she dosn't want the mod to be dependent on too many other mods, whenever an update is released.
It's not a matter of being dependent on other mods, it's a matter of "I don't like this mod or the mod's creator, so if you the user decide to use this mod alongside my mod, fuck you." It's a very passive-aggressive attempt at censorship and trying to control how John Q. User plays his game. It comes with a mindset where your personal vision of what Minecraft should be is paramount over everything else, and everyone else has to abide by that or get fucked. It's very egotistical and focused more on self-aggrandizement than on simply making something fun and interesting.
TLDR: Minecraft modders are terrible people.
E: If you can't tell, I really, really, really dislike these guys and the way they try to control how other people have fun.
Yes and all of this just goes to show how much the Minecraft folks don't care about enforcing their terms of service, Specifically these portions,
Under essential requirements;
NOT be unlawful, deceptive, obscene, harmful or disparaging
NOT adversely affect the Minecraft Brand or Minecraft Assets
Under Minecraft Terms of Service
Section What you Can Do
"If you've bought the game, you may play around with it and modify it. We'd appreciate it if you didn't use this for griefing."
Under Mojang Terms of Service
If you make any content available on or through our Game, you must give us permission to use, copy, modify and adapt that content. This permission must be irrevocable, and you must also let us permit other people to use, copy, modify and adapt your content. If you don‘t want to give us this permission, do not make content available on or through our Game. Please think carefully before you make any content available, because it will be made public and might even be used by other people in a way you don‘t like.
END SECTIONS FORBIDDING WHAT THEY DID.
BEGIN SECTIONS ABOUT HOW ESSENTIALLY FORGE and MCP CAN'T BE LEGAL UNDER MOJANGS GENERAL TOS.
"Do not redistribute our games or any alterations of our game files."--This means that Forge's Class Modifications fall under the ToS violation area.
You can't "try to make money from anything we‘ve made... (unless we specifically agree it – such as in brand and asset usage guidelines) "--The brand and usage guidelines don't cover mods making money, only YouTube videos, meaning ad.Fly links are a nono.
"Beyond that, you are not basically allowed to copy, reverse engineer or decompile our Game." -- This means that projects like the MCP and Forge which rely on decompiling and/or reverse engineering, fall under the nono list, as far as the Mojang Company ToS go.