Alright, let me put it this way.
I invent a kind of widget for using in a gidgetraption. It's an intricate little widget, not something simple. I patent it. I now own the exclusive rights to make this widget.
Bob Machines Corp likes my widget. It works really well with their gidgetraption. They pay me some money and now they can buy my widgets to use inside their gidgetraptions that they sell.
Steve Machines Corp also likes my widget. But they don't get why they should have to pay me a bunch of money for it. So they just package it up in their gidgetraptions without paying me royalties.
I can sue Steve Machines Corp for this.
This is similar to how Technic/Tekkit (Steve) steals mods (widgets) for use in their modpacks (gidgetraptions) without getting permission to redistribute them (package them up) from the creators (widget inventor), often not giving them credit (royalties), while Feed the Beast (Bob) does.
And if I'm really mad at them, I can change the design of my widget (mod) to specifically not work with their gidgetraption (modpack), and make it not start up when installed with it. If this makes people with already-existing Steve's gidgetraptions (Tekkit) angry, I can tell them, sorry, take it back and get Bob's (FTB). And unlike in my analogy, switching to FTB or MultiMC or a manual install instead of Tekkit is completely free and you don't need to go taking things back to who made them! Heck, if you want to copy over all the mods from Tekkit to FTB or MultiMC or your .minecraft folder and add GregTech that way, you can!
And it honestly baffles me why you would name a FTB folder after Tekkit. Really, that's just a little weird in my opinion, but very easily fixable. How hard is it to change a folder name?
Yes, Greg ought to have an easier way to detect Technic/Tekkit. But why turn it into a flame war?