I recently actively contributed to the AA# library.
AASharp is a C# port of PJ Naughter's static C++ library, AA+. Naughter's library implements the algorithms in Jean Meuss' book, "Astronomical Algorithms."
This library is under the LGPL license. This means that you have the right to use it (by using the DLL) both in free and commercial software. You are required to specify the following points in your software documentation :
You can use the code under following conditions :
For complete information, read the GNU LGPL License