It is basically Apache License Version 2.0 plus the "powered by wisemapping" text requirement on every single page. In few words it means that you can do whatever you want with the source code but you must keep the "powered by WiseMapping" text in every single page that uses WiseMapping code
Do I need to share my modification in the source code ?
Not at all !!!. You can do whatever you want with the source code with the only restriction of keeping the "powered by WiseMapping" text requirement on every single page. However, sharing your changing with us will make you easy to bring the latest changes introduced in the product avoiding nasty merges ;)
What if I want to remove the "powered by wisemapping" text?
Well you can do that if you have our written authorization. If this is your case, please write to us explaining why is that you need to do this, and we will let you know if you have our authorization.