I'm sorry to announce you that Collagol is over. I had a DigitalOcean droplet which cost 5€ a month, and since the site wasn't getting much attention I didn't feel like paying forever.
I hope you enjoyed it while it lasted (for a year!), and if you want to host an instance yourself, the code is publicly available here:
https://github.com/Uriopass/Collagol
See you :-)