To be fair, this isn't a Synology package, it is provided by one guy who works hard to try and get the Java Crashplan code to work on Synology. When Synology upgrades the DSM it stops working. Check out the forums to see the pain points people have to address to keep this headless client working:
It is a hack. There should be an official release from Crashplan or Synology. Same for the other big backup cloud providers. If there was something better and supported on Synology than Amazon S3 or Glacier, I'd personally be prepared to get my wallet out. These companies are missing a big market of Synology owners who are desperate for an alternative, and no I don't want to use HiDrive.
DSM 4: http://www.hanselman.com/blog/HowToSetUpCrashPlanCloudBackup...
DSM 5: http://www.hanselman.com/blog/UPDATED2014HowToSetupCrashPlan...