Laz, private packs are totally different then personal use.
To expand on this viewpoint:
[EVERYTHING FROM HERE ON OUT IS HYPOTHETICAL, NOT ACTUAL EVENTS]
Example 1: I own a server. I only want some mods on it, and I want it to be easy for my members to use and download. I do not get permission to make this private party modpack for my server. I have, lets say, a total of 50 players who are whitelisted on my server. I ban one of them. They get pissy and redistribute the modpack that I put together (without permission) so that all of their friends have it too.
Example 2: I own a server. I only want some mods on it, and I want it to be easy for my members to use and download. I do receive permission to make this private party modpack for my server. I have, lets say, the same total of 50 players who are whitelisted on my server. I ban one of them. They redistribute the modpack (or in FTB's case, the pass code) to their friends.
Both examples result in a disgruntled player redistributing the mod packs. The big difference being, in example 1 I act completely disrespectful, in every aspect, to the modding community as a whole, whereas, in example 2 I respect the wishes and talent of the people who worked on it.
As I stated before, it's rude and disrespectful to take things without permission.
Let's take the same concept and apply it to a different aspect of life: My friends dad buys himself a pretty new car. I really want to take it for a spin. The keys are in the ignition, in his driveway, the car is unlocked. I take the car. You know what's going to happen? I'm going to end up having the cops called on me for stealing his car, regardless of intent.
For those who have a hard time with analogies: the car = mod, the keys = the mod being downloadable. What happens? I stole the car.
Or, the example I gave during my last discussion about this. I write a program (in this case a mod). I upload this program (mod) to a website (such as github, or MCF). You download it, with intent to redistribute (taking a mod to include in a modpack). You did not ask if you could use/redistribute it. No credit is given, but now, you suddenly have a virus on your computer. It's not my fault. You took it, with the intent to redistribute. You never asked if you could, nor did you give me credit for the creation. Sorry pal, you have no one to blame for your now dead computer.
The last example is a little rough around the edges, but the coin has two sides. If I can take credit for something, I can also take blame for the aftermath.
But as said earlier in this discussion, it all comes down to respect for the mod authors. I don't think I could ever have the skill set that these men and women use to make their mods. I hope one day to learn even a fraction of the knowledge that they have. Until then, you can bet I respect the skills they put into the work they do.
(This next part actually happened, it is not hypothetical)
An example regarding the idea of respect. Prior to my husband asking me to marry him, he asked my father for permission. Out of respect. Now, my family respects my husband for his past actions.
It's a two-way street. Respect is just like trust, you don't just get it because you participated. You have to earn it.
Edit: Any further opinions of mine that are given after this statement, and referring to this statement, have a high likelihood of being opinions regarding issues in society as a whole.