So if you want to play Crackpack (or any other modpacks in the Curse/FTB launcher) without having to open the annoying Curse app, here's what you do. First, you do need to install Curse and download the modpack you want. Run it once (just open the launcher; you don't actually have to hit play from the Minecraft launcher). Once it's installed, go to the Settings button in the Curse app, click "Minecraft", and then copy the address listed as "Minecraft Install Location".
Next, open Notepad/TextEdit (or your text editor of choice). If you're on Windows, copy-paste the "crackpack.bat" file below into your text editor. If you're on Mac or Linux, copy-paste the "crackpack.sh" file below into your text editor (warning: haven't actually tested this one). On the first line, replace "REPLACEME" with the address you copied from the Curse app. Then save it as "crackpack.bat" or "crackpack.sh". On Mac/Linux you might have to open a terminal and run `chmod 700 crack