If you have an existing Eclipse installation and simply wish to install Acceleo in it, you can install it from one of the Update Sites, available here https://download.eclipse.org/acceleo/updates/releases/4.0/.
When installing the update site you must ensure that "Contact all update sites during install to find required software" is checked and that in the "Manage…" dialog, the "Latest Eclipse Release" update site is checked.
For a minimal installation you can select the following features and plugins:
For those of you who need to retrieve the source code of Acceleo, it is available on Github: https://github.com/eclipse-acceleo/acceleo/.