If you have an existing Eclipse installation and simply wish to install Acceleo in it, you can install it from the Update Site, available here https://download.eclipse.org/acceleo/updates/nightly/.

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.

Install Acceleo

For those of you who need to retrieve the source code of Acceleo, it is available on Git: https://git.eclipse.org/c/acceleo/org.eclipse.acceleo.git/.