This library is a client to the Fortnox API (www.fortnox.se), the library can be used to connect to the Fortnox API and to call methods in the Fortnox API.
The GNU General Public License (GPL) is well suited for applications but is problematic in libraries since it requires any application that links to the library to also release the source code for the application under the GPL.
Consider changing license to another license such as the MIT License.