I've written a linux application that interfaces with a lot of GPL software. My application is written in javascript/HTML/CSS/python and uses MariaDB on a CentOS 7 platform (it also uses jquery and a few simple third party tools); we would like to sell this on our hardware as an appliance. The GPL software we are interfacing with (usually via command line or configuration files) include those mentioned above along with lots of little linux tools (e.g. yum, hdparm, psutils and lots of python modules etc…).
We do not want to publicly release the code we have written, even though it would be pretty easy to reverse engineer a lot of it due to our programming language selections (obviously). We intend to lock down the command line, its to dangerous for our clients to access. We will happily direct the users to where they can download all the GPL software, that we aren't modifying, if we are required to; but we don't want to direct them to our software… why would they pay for software updates if they can get it for free? We couldn't survive like that.
So, assuming you say yes I have to issue the software I write under GPL, how can this be avoided and how much will it cost per distribution… do I have to pay the developer of every little tool I read from or write to? It would seem impossible to manage. MySQL seemed to indicate that I do have to pay them in one area of their site without telling me the price, then that I didn't have to pay them in another area.
I have read GPL many times, and have been researching for months… I still don't understand what I need to do, if anything, to achieve my intent of not having to give my software away (other than get a lawyer we can't afford to tell me). For example, could I sell the appliance with the GPL software on it (using the GPL license), then sell our software separate under whatever license we please? If so, does that mean I only need to make sure they are separate line items on our quotations?
Best Answer
You better get proper legal advice, but if you can avoid linking with GPL software, you can usually avoid distributing your source code. If you are linking, you don't really have any option other than to distribute your code.
This is probably the best guidance you can find:
http://www.gnu.org/licenses/gpl-faq.en.html#MereAggregation
In general, if you can interface with the GPL software only via command line, HTTP requests, etc. you may be safe.