Can you suggest a software tool (with GPLv license) to perform load testing for a Web server?
Curl will allow you to run through a sequence of URL quite easily. i.e.
curl -s "http://google.com?[1-1000]"
This will make 1000 calls to google i.e.
http://google.com?1
http://google.com?2
etc...
You can then add these calls to a script and run them consecutively as background jobs. There's a full explanation of this http://servermonitoringhq.com/blog/how_to_quickly_stress_test_a_web_server