Person A still have the IP of the software IMHO, so person A can do whatever with the software. Person B still have the latest-before-relicensed software, person B can fork or create new software based on latest-before-relicenced software.
Similarity like Qt software company doing the relicenced thing and Illumos project keeping latest-before-relicenced software.
Similarity like Qt software company doing the relicenced thing and Illumos project keeping latest-before-relicenced software.