Sure, but an idea is not a (physical) good, nor is it a service. Coming up with an idea or writing a book is a service and should be paid for (probably by commission), but (and Stallman would agree) the idea or book itself should be free.
He was also famously staunchly against proprietary software in any way, so therefore he wouldn't have been spending money on software unless there was no other option that came close to meeting his needs.