The concept is not new, but Reaction is probably the closest to a commercial implementation. Also, it's not fair to compare it to the jet when RBCC isn't a fundamentally novel form of propulsion, just a combination of existing ones (like a car that is both gas and electric propelled). This is not something that could supplant the jet.
Some people are comparing this to SpaceX's pure-rocket approach. Up until yesterday, SpaceX and Scaled were working on their own type of combined-cycle launch with Stratolaunch: http://www.flightglobal.com/news/articles/stratolaunch-and-s.... The difference is that the jet and rocket would be separate vehicles instead of fitting into one nacelle. It'd have some of the advantages of using air as propellant as with a RBCC engine, but easier to design I think.
It is combined cycle, but that does not mean it's equivalent to the RBCC design. There are several variations of combined cycle engines. RBCC is not a catchall. This is a refinement of the Liquid Air Cycle Engine concept that was researched by the US military in the 60's and the british in the 80's. The principal british investigator was Alan Bond, who is also the principal in Reaction.
It is appropriate to distinguish it from both jet engines and rocket engines because in the Brayton Cycle compression is adiabatic rather than diabatic in SABRE. I don't believe there is a formal term for this cycle, but the closest existing would be the Ericcson Cycle.
I do not understand your preoccupation with whether to categorize something as novel or not. The have a chiller that drops the temperature of a near supersonic air flow over 1000C in a fraction of a second. If that doesn't meet your standards of novel I don't know what would.
The precooler / heat exchanger is the SABRE's distinction. Ramjets and scramjets don't have such. It enables low internal gas velocity and small compressors and more thrust from a smaller engine and higher top speed than jets.
It's like saying when the Wankel was invented that "it's just another internal combustion engine". Sure, it is, but it's quite different from most of the others.
The Stratolaunch craft could be used to launch suborbital rocketplanes. You could have the 21st century counterpart to the Concorde, going over twice as fast, combined with space tourism.
It is appropriate to distinguish it from both jet engines and rocket engines because in the Brayton Cycle compression is adiabatic rather than diabatic in SABRE. I don't believe there is a formal term for this cycle, but the closest existing would be the Ericcson Cycle.
I do not understand your preoccupation with whether to categorize something as novel or not. The have a chiller that drops the temperature of a near supersonic air flow over 1000C in a fraction of a second. If that doesn't meet your standards of novel I don't know what would.