The same as the current CPU-Miner program that you can download seperately?
I wonder why the original users didn't mine? What else could you do with it the first few months?
No, the same as the one that's included in the official client.
The reason for not mining would be turning off computer at night, not wanting to waste cpu, forgetting to start bitcoin after reboot etc. Since they were worth practically nothing the incentive for generating coins were low.
I generated for a short time when I first discovered bitcoin, but then I forgot about it for some months, and never started generating again, since getting maybe one block every few days was not as fun as getting 5-10 a day.