I'm about to start upgrading subscribers to Dwarf Fortress 0.44.12 now. Sorry it took so long, I have discovered an issue affecting this upgrade and further version update processes, and had to find a solution first.
In order to perform the upgrade, you game will be saved and server terminated. The next time you connect, a server with DF version 0.44.12 will be started and you'll need to load your game manually. This will be done even for new subscribers already having version 0.44.12 to ensure everyone's servers are running the same code.
I have made backups of all saves and running games before the upgrade, please let me know as soon as possible if you notice any problems after connecting to your upgraded server. Also, some games are in a state in which it's not possible to save them (most comonly world generation and embark preparations) - they will upgraded once they can be saved.