[ptx]

Only phones sold by carriers were controlled by carriers. You could easily (in Europe at least) buy an unlocked phone and put in a SIM from any carrier of your choice. You could then easily install (i.e. "sideload") Java apps from anywhere you wanted, e.g. from a storage card or over Bluetooth, although some permissions were restricted unless you bought an expensive code-signing certificate.

[dangus]

As I recall, in the US at the time the best networks were CDMA and had more strict device activation requirements, especially Verizon.