There's an explanation at  regarding installation of an Early Access edition of SpringSource Tool Suite in Eclipse Juno (4.2) milestone builds. That page is dated 14 March, 2012. The explanation at that page provides thorough instructions about how to add the necessary update sites to a Juno installation, for adding the SpringSource Tool Suite to that installation.
One of the update sites listed is . Presently, upon accessing that URL, one receives an XML formatted 'Error' document with an 'AccessDenied' code - full contents as follows:
It appears that this prevents the installation of the SpringSource Tool Suite into the Eclipse Juno (4.2) platform, by the methodology described at .