a library for big integers, rational and complex numbers.
The ExtendedArith library itself is based on another library, the GNU MP (GMP) library which is written mostly in C but also in assembly. This library has the advantage of being distributed under conditions of the GNU General Library Public License(GLPL).
By using the ExtendedArith library you will become a licensee of the GMP library as well. The GLPL is quite liberal, but it imposes certain restrictions. In general, if you redistribute the GMP library (as a part of something else) you have to ensure that everyone you is still able to apply changes that part of your code. In particular: If you create an executable Clean program that uses the ExtendedArith library (and hence the GMP library) you are not allowed to give the executable to someone else without giving him the source of the GMP library, including documentation about all applied modifications (yours and ours). See the LGPL http://www.fsf.org/copyleft/lgpl.html for further details.
You can also download our (modified) source of the GMP library from our server.