I wanted to know if trimmomatic can only be run on GNU GPL v3 or it can also be run on windows environment? I am new to bioinformatics and I have no much knowledge of basic informatics neither.... I need to trim fastq files.
Trimmomatic is a Java application, and probably can be run on windows (see, for example, this discussion at Introducing the Trimmomatic). However, you will find few (if any) help around if you encounter problems. I would advise you to use Linux, or install the Windows Subsystem for Linux, in case you are using Windows 10.
GNU GPL is not an operating system, it is a software license - by the way, Trimmomatic is licensed under the GNU GPL v3.