Oracle Broadens Support for Open-source R Analytics (PCWorld)

Indeed. As always, with GPL-licensed works, it helps to think of the running system and then the act of the user exercising the right to see and modify (and distribute) the code for that complete system (down to a certain level as noted in the licence).

If there's a portion of the code that is proprietary and this was bolted on (using dynamic linking, perhaps) under the user's own initiative, then they have chosen to be able to exercise their rights for only the part that has the copyleft licensing: no-one has made any promise to them about the proprietary part of the resulting system.

On the other hand, if the proprietary code was provided and is loaded into the system under someone else's initiative, that party has committed to letting the user exercise their rights for the whole system. If that other party withholds those rights for the proprietary code then they have violated the licence of the GPL-licensed work by distributing it in such a configuration.