There is information on the Internet (here for example) about using the PPA ppa:moorkai/cinnamon to get Cinnamon 2.6 installed on Ubuntu 15.04. I'm noticing that that the install fails, as it requires libcjs0 at least 2.0.0.
If I install that package manually, attempting to install Cinnamon then results in a failure about the cjs package. The setup of those packages won't let me have libcjs0 and cjs packages installed at the same time; each insists on the removal of the other.
I could force the install of one of them, but that seems undesirable given that I really don't know what the packages do or what they affect.
The install from ppa:gwendal-lebihan-dev/cinnamon-nightly does work. (Well, the installation works, but the desktop environment is completely unusable; something's obviously wrong because it's just broken.
I'm moorkai. I received a few e-mails with complaints about the PPA not being usable, but I really didn't expect so much users will try to install Cinnamon from my PPA ... and fail due to my sloppiness. I guess I deserve the bashing from the commenters then. I am sincerely sorry for all the inconvenience caused. I had some issues with the Launchpad system refusing my uploads, but I'll provide a (hopefully) adequate workaround. If everything goes well, the packages ought to be up in less than a few hours.