A software licence is a legal way to distribute (or redistribute) software to users who want to use it (or redistribute it).
Software licences are required because all software is protected by copyright.

How do you use a free or open source licence for your software?

The terms open source and free software stand for the same kind of licensing model, which is model that can be pursued using licences such as the GNU General Public Licence (GPL).

What constitutes "free software" can be described very clearly. The inventors of this licensing model (i.e. the Free Software Foundation - FSF) have pointed out clear definitions of what a free software licence must fulfill.

Free software is software is only free if it

• can be used freely by anyone
• can be used freely examined and adapted to adapted to one's own needs can be freely copied, distributed and 
• can be put online 
• can be freely modified and further developed and the improvements can be made available to the may be made available to the general public

The definition implies that a free software licence gives everyone a simple right of reproduction, distribution right, the right to make works available to the public.

In the Refubium, you can use in the metadata form the following licences.

Name	URL
MIT License	https://opensource.org/license/mit/
Apache License 2.0	https://www.apache.org/licenses/LICENSE-2.0
2-Clause BSD License	https://opensource.org/license/bsd-2-clause/
3-Clause BSD License	https://opensource.org/license/bsd-3-clause/
GNU General Public License v3.0	https://www.gnu.org/licenses/gpl-3.0
GNU Lesser General Public License v3.0	https://www.gnu.org/licenses/lgpl-3.0