ZDNet noted that this kind of software isn’t strictly new, and GHIDRA in particular isn’t secret (it mainly entered the spotlight with the Vault 7 leak). However, existing reverse engineering options like IDA are expensive and generally inaccessible — this would let any reasonably knowledgeable person tear open a program and gain a better understanding of what makes it tick.
As with the NSA’s other open source projects, this isn’t an altruistic gesture. In addition to improving overall security, it could improve the quality of GHIDRA by letting the community address bugs and introduce their own features. Whatever the NSA loses in control it might gain through better overall security.