And, in my personal opinion, if you had used the proper framework to start off with, this would be a non-issue and natively cross-platform compatible. Unfortunately, at this time it would be pretty much starting over from scratch and not worth the time or effort for the 2% of us who are Linux.
A thing about that 2%... make it less viable for a platform, and less people on that platform will use it. I haven't downloaded or updated FTB in months because I've been using ATLauncher/MultiMC since they are both native linux compatible, and quite frankly none of the packs on the FTB launcher have really tickled my fancy enough to encourage me to update my FTB Launcher. Actually... checking my files, I have literally not updated FTB in over a year. Wow. So if you had made it linux compatible, you might've ended up with more people on linux using it. Probably not enough to warrant doing it at this point, admittedly, but just sayin'... looking at how much business you might get from 'competitors' by doing something is also occasionally a good idea. Or maybe not, I'm not very familiar with your business model.
So yea, zero interest in Curse Launcher since it won't run on the OS I run. It's got a lot of good features, I absolutely love the mod devs getting downloads when a pack including their mod gets downloaded, that's a thing that needed to happen. But as far as the rest? Eh. I tend to be a cantankerous, anti-social old geezer, so the friend thing is actively discouraging for me, although I will grant that I may be in the minority on that point of view as well.
I'm not against centralization of mods in a place like Curse, actually. By requiring mod authors to give permissions to distribute by putting the mod on Curse, you make mod pack creation MUCH less of a legal headache (speaking as one who dealt with said headaches previously), which is a MAJOR benefit. This gives an easy litmus test of Curse = yes I can include without having to track down the mod author, get perms, document said perms, and keep said perms up to date. I like this, as it is a benefit to both mod pack creators and the mod authors themselves. So having a single repository for all mods available on mod-packs? Amazing. All the yes. And if a mod author decides they don't want to give those permissions... that's entirely his right and decision. He'll just be left out of Curse and all of the benefits Curse members enjoy.
All I want is a easy way to grab ftb packs on linux without mucking about on Google. I don't care if it's command line or a GUI. Command line, I can create a BASH script to do the syncing for me in less than 2 minutes. Heck, make it possible to add the repos containing the packs to our mirror lists in our package managers. That would be the most ideal solution IMO.
To add to this: All we really need is a regularly updated script grabbing from the repo each pack. Would need bare bones bash knowledge and a minute or two for each pack, if you don't just automate it. Pretty much what the launcher already does, but in BASH.
Actually, that might be done better with a PPA, particularly for something like Mint's Update Manager. More user friendly on the other end, and things like Mint's Update Manager can grab hold of it and let the end-user know there's a new update for download. And it would download FROM THE CURSE PAGE so the mod author gets the download credit. It would be the best of all possible world for Linux users.
I'd be tempted to hack out something, but I'm too busy these days, and I am still of the opinion that Microsoft is just going to hijack everything once it becomes profitable enough for them to do so. I honestly feel sorry for the Curse crew, that's gonna suck when MS gets around to bothering with enforcing their ownership.