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Old 17-10-2012, 16:34   #1
Pep
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Need some direction to use OpenCPN and respect GPL

Hello,

We are currently designing a little software to program an auv and need a software to program course via waypoints.
I just discovered OpenCPN that has really excellent features and performance and I was thinking to interface with it.
The programming software that we designed is closed source. So my question is how I could interface with OpenCPN with respect to GPLv2 license, keeping some parts of my code closed source.

I need to display S57 maps in openCPN, click on it to put waypoints.
Then I want to send my waypoints to my specialized app (closed source).
Is it ok to open a tcp port in openCPN and send waypoints via TCP channel? Perhaps there will be communication in other direction, to say waypoint is OK/Bad etc...

I read, that another option could be to do a plugin to openCPN. Can this plugin (specialized for my specific hardware be closed source?).

Off course, any code written for OpenCTN itself (tcp channels or anything else) will be released as GPLv2.

Regards,

Pep.
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Old 17-10-2012, 17:08   #2
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Re: Need some direction to use OpenCPN and respect GPL

Hopefully you already know that O's GPL2 license only applies to O, not to any other software that's present on the system and talks to O through files or serial ports or sockets or whatever i/o mechanism.

And as you say, changes to O will need to be open sourced per the GPL2

Remains the question of plugins, which Dave has outlined here: Widespread Adoption of OpenCPN

In short: Closed source plugins are accepted but will not be hosted on opencpn.org.

This is based on GPL2 Section 0: "...Activities other than copying, distribution and modification are not covered by this License; they are outside its scope. The act of running the Program is not restricted,...."
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Old 17-10-2012, 19:34   #3
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Re: Need some direction to use OpenCPN and respect GPL

If you plan to use any segment of the GPL'd code of OpenCPN, you need to keep the GPL license in all you code. There are variants (LGPL for linking libraries, AGPL, etc) that have slightly different limits.

Other open source (but not free software) licenses, such as BSD allow privatization/closing.

You must be aware that one of the purposes of the GPL and related licenses is precisely to impede the privatization or closing of software developed as free software. Otherwise, software developed by the authors as an offering to the community would be exploited for profit by unrelated people.

A different issue is if you communicate, say via pipes, sockets, files, ports, messages, shared memory, etc, with the program. In that case your code need not be GPL.

To date, no court challenge to the GPL have been successful, and all violators have agreed to make the source available. Recent cases involve router makers, for example.

Diego
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Old 18-10-2012, 02:17   #4
Pep
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Re: Need some direction to use OpenCPN and respect GPL

Thanks JesperWe, that confirm my initial thought.
It's also good to see the "openess" of the plugin system that I think will help widespread OPCN.

Dear dpons,

As I'm also opensource developer outside of my job and I'm just asking how to do things well. I don't want to stole any work and I will give back to community as I always did in the past.

Hope I will be able to contribute back to OPCN interesting features .

Regards,
Pep
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Old 18-10-2012, 09:20   #5
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Re: Need some direction to use OpenCPN and respect GPL

Quote:
Originally Posted by Pep View Post
As I'm also opensource developer outside of my job and I'm just asking how to do things well. I don't want to stole any work and I will give back to community as I always did in the past.
Pep:

I didn't mean to imply that at all, I was just exploring the issue as many people are tempted to mix free and closed software.

All the legal implications of copyright an patent law are so confusing, and everytime I hear Stallman I grow more confused. I also develop free software, and mainly used free software in my corporate consulting days.

Diego
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