laravel

According to the the readme file (https://github.com/laravel/laravel/blob/master/readme.md) it is under the MIT license which is considered to be a perfectly free software license.
So don't hesitate to use it.

Normally in the git repos there is a file called "LICENSE" or "COPYING" in which you can see which license holds or this information can be found on the project homepage.
Once you have the name of the license you can search wikipedia and look up whether it is free or not.
Sometimes the name of the license cannot be found, then it is best to ask in this forum.

And sometimes something claims to be under a certain license but actually isn't, e.g. the Linux kernel... :-/

(supposedly GPL'd but contains binary blobs)

So the only way to be relatively sure is to see if it claims to be under a free license and even if yes then go looking around the tree for files which don't comply with the license or even come with a license of their own...