You'd have to ask them. If they are intent upon offending everyone and challenging their worldviews, the statement is sufficient, isn't it?
The Gospel is not about what we do, but what Christ has done for us. If Rev. Warren's goal, as should be the goal of all Christian pastors, was to preach the Gospel, he failed. What he likely did do in his repeated mention of his buzzword "purpose" was to peddle his book.
Have you submitted your idea for a quote to Starbucks?
If you have done something noteworthy with your life, as Rick Warren has, maybe they will use your quote.