The mbed OS takes up a scant 256KB of memory or less so it can be installed on tiny devices such as sensors. It includes C++ programming interfaces, an event framework, a communication manager and support for cryptography, among other things.
ARM says most, but not all, mbed OS software will be open source. In theory, Imagination or Intel could port mbed OS to their own chip architectures if they wanted to, though ARM made a point of saying it's free for use on ARM chips, implying others would need to pay a fee.
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