Was it also possible to generate/produce STEEM or SP with it?

Yeah, it was possible. I brought in a few hundred SP that way. If I remember right, they had 19 slots for the primary witnesses, 1 slot for an alternate witness, and the 21^st slot each round went to a proof of work miner.

Unfortunately, someone managed to hack the algorithm, and a single miner was dominating the PoW mining queue (@supercomputing and @supercomputing01-99 accounts, or something like that... see here). They tried to fix the algorithm a time or two, but kept having problems so they disabled it and went to 100% DPOS. No idea who the account owner was, but they brought in a nice rake...