If here are no bids, will program still work and bid opening bid for me? Or, if I already have highest bid, will it just let it go and not bid up, so I will win?

If a snipe is set, JBidwatcher always tries to bid at the end of the auction.

If there are no other bids, JBidwatcher will still place a bid, and if nobody else bids against you, you will get the item at the sellers minimum bid price.

If you are already the highest bidder, the bid placed at the end of the auction will not affect your existing high bid.

There is an exception, for example if you bid $20, and some other user comes along later and bids $20, then you will be the high bidder as exact ties are resolved to the earliest bidder. If you come back and up your bid to $25 after that, for example via a snipe, then eBay consider you bidding against the other (later) bidder, and will ratchet up the bid to one minimum bid increment higher ($21, if I recall).

Ties and near-ties are one of the more confusing parts for new eBay users, but in all other cases JBidwatcher's bid will not affect the current price if you are high bidder.

An important feature I think you might have missed is the way eBays bid process works. It is a specific type of auction, a 'highest bidder, second price' auction.

What this means is that the highest bidder always wins, but they only pay a price based on what the second-highest bidders price was. So if you bid $1000, but the next highest person bids $10, you'll only have to pay $10.50, which is one minimum bid over the 'second price'. This is not just true of sniping, but of the normal bidding process on eBay as well.

This is why JBidwatcher doesn't need a lot of time at the end of the auction, to place lots of bids. It just places the one bid, your maximum, and lets the underlying system manage the 'second price' nature of it.