It's definitely an interesting business model. I've wondered how successful an enterprise open-source software can be, with just official support/ convenience being the major area of revenue. I'd like to believe that if I were ever to release a product I'd open-source it and be willing to take the financial risk... but in reality it would be very difficult. RHEL is definitely "inspiring."
RHEL does it well using the "FOSS software and pay for support" model. Other companies usually open-source the majority of the code, but keep some features closed source to make revenue from. Some use the even less common method of selling a compiled version, and releasing code under a very restrictive license in an attempt to get you to buy the compiled version as it's "easier". I personally like RHEL's method. Good article too
