The internet doesn't exist in SW, so likely things are based on physical modules; so he probably scavenged, repaired, or assembled a physical module that embodies the droid's mind and everything is more or less hard-coded. And because the internet--and perhaps copyright law--doesn't exist, he doesn't need to activate the module with a central server.

I don't really even think programming is touched on, it's more just based on electronics. Software isn't really at thing.

[Edit: I mean, obviously software exists, but it doesn't function like real software does in the world. Tech is largely based on droids, which are delightfully physical and embodied for a visual medium, and droids are more like artisanly-modified cars than software that can be updated and copied. That is to say, the technology in Star Wars takes a lot more cues from mechanics and electronics than it does from software and programming. It is a markedy and consciously retro type of future (or should I say "past?").]