A question regularly asked ....

"What guarantee do I have that [state name of a piece of open source software] will remain freely available to me?"

Open Source software is distributed with, and subject to, a license - usually the Gnu General Public License or something similar.  The GPL differs from other software licenses in that it gives you rights and assurances, rather than seeking to restrict you, whilst at the same time protecting the authors of the software from someone patenting the ideas that they are giving out for free.

Amongst the rights you are given under the GPL are rights to use, copy and even modify the software - you have an explicit right to  actually get at the source code, and it's explicitly stated that the rights can't later be revoked.
Turns out that as well as being free, you have a darned site MORE guarantee of a long life for open source software that you have for commercial code.  Case in point - we have a superb specialist old scanner.  Hardware is fine, but the software drivers ONLY run on an OS that's no longer supported.  With open source access to the driver code, I could get it running on one of our regular systems rather than having a computer in the corner with an old O/S, used only to support the scanner these days.

---