Tony,
Don has said, since the beginning in 2022, that he (SonicScores) would sell and support ONLY NEW VERSIONS of the PassportMusic catalog. So, it is unlikely that he would answer you – if he ever comes to visit this forum before the time new versions become available.

There are two methods to explore:

– musica.at – who is/was an authorized reseller of the PassportMusic (previously GVOX) is still selling licenses for Encore 5. Their catalog does not show show MasterTracks (nor MusicTime), but they might still have a few licenses left. Best is to ask Johannes Kaiser-Kaplaner via their contact form https://www.musica.at/encore/index1.htm

– obtain a second-hand copy from a legitimate user who does not need it anymore. Just as you buy a second-hand book (or car, or house…).
The laws in his country (not yours) may allow that, and supersede a restriction on reselling (or giving) specified by the EULA (end-user license agreement).
This would be the case, under certain conditions, in the EU.

You might just get surprised and MTP could skyrocket with the current producing crowd. None of the current MIDI sequencing/DAW apps (i.e. FL Studio, etc.) come close to the elegance, depth and ease of use of your original Master Tracks. I hope you keep the original interface design: simple yet complex, like it was… that’s MTP’s strength – like sculpting with chisel and hammer. (And please keep/add device files for easy mapping (Korg M1. XD5, etc.) 🙂