What files need to stay on the device for a clockworkmod? I installed a clockworkmod months ago to an Alcatel OneTouch 995. On the SDCard there is still a clockworkmod folder. The directory structure looks like follows:

└── clockworkmod
    └── backup
        └── OT995_4.0.4-FR
            ├── boot.img
            ├── custpack.ext4.tar
            ├── nandroid.md5
            └── system.ext4.tar


I wonder if the folder needs to stay on the card. Can you please explain why or why not?
The clockworkmod folder contains data that CWM created, and more specifically the backup folder is where your device's backup files are stored. All of those files are what constitute a Nandroid backup of your device. 

If you're looking to free up some space on your device you can delete the folder, but CWM will recreate only the folder every time you reboot; the backup files will not be recreated, and will only be generated when you use the Backup feature so be sure to copy these files to a computer (for backup purposes should you ever need to restore it).

I often create Nandroid backups, copy them to a computer or external storage, and then delete them from my device to save the memory for more useful things.