Normally radios are built out of discrete electronic parts using mixers, filters and paths for specific frequencies and various modulation modes.
SDR on the other hand can change the modulation programmatically without changing the components and topology. Very handy in space if a new modulation standard gets adopted by some goverment agency.
This is not about SDR, it is about "software defined satellite". It is a generalization of the SDR concept, involving the whole satellite. Basically, it is about designing a more configurable satellite, suitable for a wider variety of tasks.
Seems the "software defined" in these things are mostly about reconfiguring antennas and radio beams. It's perhaps a bit more than a traditional SDR, after all there's not much modern radio communication not using SDRs, even the Mars rovers and satellites have them.
According to the press release, it is just a spaceborne SDR together with a very configurable antenna array, which can be used to provide various kinds of communication links.
But I think the space industry tries to communicate something other than SDR when they are talking about software-defined satellites. E.g., satellites as a service, allowing different customers time share a satellite and use it for different purposes by making the capabilities wider.
For now, the configurability of the sattelite appears to refer to using a configurable antenna array, which allows the configuration of a variable number of beams, in various directions, and with various directivity properties, presumably besides an SDR.
