AstroSource is a free, open-source program to erect a natal chart (horoscope). Using one or two dates and locations, it generates a simple or combined chart, whether for synastry or transit. Chart is placed on the left side and the point list is placed on the right side. The generated picture is clean and easy to read, with no overlapping symbols.
The software is licensed under Swiss Ephemeris Public License (SEPL). Swiss Ephemeris API is property of AstroDienst AG (http://www.astro.com). While the program is open-source, the Swiss Ephemeris API is not. Horoscope making and calculations are complex, this API indeed being a convenient wrapper. Even though the exact calculations are undisclosed, you can learn a lot about chart drawing inspecting my source code.
The program generates the following report (data is taken from my own natal chart, birth date 31-jul-1982, time 20h45min, coordinates for Belém, Pará, Brazil. English only):
Chart details Elements: Fire 5 Earth 0 Air 3 Water 4 Rhythms: Cardinal 5 Fixed 3 Mutable 4 Polarities: Positive 8 Negative 4 Houses: Angular 5 Succedent 4 Cadent 2 Hemispheres: North 4 East 2 South 7 West 9 Planets: Sun 08 Leo 25, House 05, Dignified Moon 25 Sag 09, House 10 Mercury 15 Leo 42, House 06, Fall Venus 13 Can 37, House 04 Mars 28 Lib 35, House 08, Detriment Jupiter 02 Sco 07, House 08 Saturn 17 Lib 01, House 07, Exalted Uranus 00 Sag 36, House 09, Retrograde Neptune 24 Sag 36, House 10, Retrograde Pluto 24 Lib 19, House 08, Fall Node 11 Can 57, House 04 House cusps: Ascendent: 16 Pis 02 House 02 18 Ari 18 House 03 19 Tau 18 House 04 18 Gem 03 House 05 15 Can 52 House 06 14 Leo 50 House 07 16 Vir 02 House 08 18 Lib 18 House 09 19 Sco 18 Midheaven: 18 Sag 03 House 11 15 Cap 52 House 12 14 Aqu 50 Aspects: Sun Conjunct Mercury Moon Sextile Mars Moon Conjunct Neptune Moon Sextile Pluto Mercury Sextile Saturn Mercury Quincunx Ascendent Mercury Trine MidHeaven Venus Square Saturn Venus Conjunct Node Venus Trine Ascendent Mars Conjunct Jupiter Mars Sextile Neptune Mars Conjunct Pluto Jupiter Conjunct Pluto Saturn Conjunct Pluto Saturn Quincunx Ascendent Saturn Sextile MidHeaven Neptune Sextile (Exact) Pluto Node Trine Ascendent Ascendent Square MidHeaven Aspect count: Sun : 01 Moon : 03 Mercury : 04 Venus : 03 Mars : 04 Jupiter : 02 Saturn : 05 Uranus : 00 (unaspected) Neptune : 03 Pluto : 05 Node : 02 Ascendent: 05 MidHeaven: 03