I'm not a developer but If you talk of the Digium HPEC, it is both commercial and closed source so Elastix wouldn't distribute the binaries.
You will have to go to Digium and pay the fee (if needed) and then download and install the key to the binary (their instructions are very precise and if you don't do it exactly their way you might be stuck with hardware that doesn't EC.)
My understanding is that the binaries are cpu specific, Yossarian might ask with some logic and insight, 'which one of their binaries would you have Elastix "drop in" the dahdi directory at "compile time" ?'
Further, you get free licenses with "relatively new" genuine Digium Boards, they care not to support older sales.
Elastix is open source, HPEC is not, if you accept their license terms, surely the onus is on you and Digium, not Elastix, to make it work?