Upon purchase of one year subscription of Express Star Teller, the subscriber is asked for relevant details of date, time and place of birth. This information is used to generate a varshaphal and predictions are made using a commercially available software – Parashara’s Light 6.0. From the printout, it looks like a computer generated report and a lot of manual effort does not seem to have gone in. Parashara’s Light 6.0 is available for a price from GeoVision Software Inc. and you can find the details here.
When I am at home and an Internet connection is not available, I sometimes use Jagannath Hora software to generate horoscopes, which I have installed it on my PC. While you get prepared to download a software, please download the full version, which is about 56MB. It is a pretty good software considering it is free.
Still, the free jyotish kundali software on this site will give you most of the information required to make predictions. It gives longitudes of the planets, rashi, bhava and divisional chart placements, nakshatras and vimshottari dashas. Since it is a java application that needs to run in a browser, there is definitely a constraint on size of screen and the application itself.
In any case, any software on astrology whether free or not, is not the end by itself. It is just a means to an end. Please do not get bogged down by the amount of information provided by such softwares. Most astrologers look at just some of the parameters. They rely a lot on their intuition, judgement of the situation at hand and most importantly, plain common sense. Advanced calculations are used just as an aid to reinforce the intuition.