I'm using ubuntu. Is there a PPA?

Yes, for stable releases. In the future we will might add a separate PPA for unstable builds.

The PPA for the latest stable release is here: https://launchpad.net/~makehuman-official/+archive/ubuntu/makehuman-11x

To enable it, run

sudo add-apt-repository ppa:makehuman-official/makehuman-11x
sudo apt-get update

Then, to install makehuman, run

sudo apt-get install makehuman

Also revere to the documentation of your operating system about the general use of PPAs!