LinuxPLC programs also Open Source?

  • Thread starter Juan Carlos Orozco
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Juan Carlos Orozco

I was thinking about LPLC and began to wonder if the programs that will run on LPLC will have to be open source. There are certain machine manufacturers that want to protect their know how by not opening the source code for their programs. Siemens PLC (I don't know about the other brands) for example recognize this need and has the option to protect the code that runs on the PLC using passwords. My question is, because of the GPL license of LPLC the programs (i.e. Ladder Logic) that run on it will also have to be OS? Juan Carlos Orozco _______________________________________________ LinuxPLC mailing list [email protected]

Curt Wuollet

No, I don't believe so. There are GPL provisions for this as there are commercial products that run on Linux apparently without violation. It would be a good subject to research as this may require that we link a certain way or some such. I myself think that there are very few ladder programs so unique, so extraordinary, that it warrants much concern, but I recognize that it would be held against us and used for FUD value. Most of the time this is just used for leverage to get the customer to buy support and enhancements only from the original provider. We can't require that the applications be GPL. I would hope that people who use our system would be the more enlightened and sympathetic to the OSS cause but we must accomodate those who want to work that way as there are occasionally valid reasons. Regards cww _______________________________________________ LinuxPLC mailing list [email protected]

Greg Goodman

There's an excellent article in the latest "Open Magazine" that discusses the limits of the GPL. The issue you raise is covered explicitly. The article points out that > The GPL doesn't use the word "combination." It uses the phrase "contains or is derived from." These terms have very specific meanings under copyright law ... [snip] > Simply combining a copyrighted work with another work does not create a derivative work. The original copyrighted work must be modified in some way. [snip] and goes on to provide a relevant example: > Consider the scenario where the Linux operating system, a GPL-licensed program, loads and executes a proprietary program. The Linux program is not modified; it is merely used for the purpose for which it was designed. The proprietary program does not "contain" nor is it "derived from" Linux. Linux does not infect the proprietary program, and the proprietary program does not become subject to the GPL. I think the article's worth reading: Regards, Greg _______________________________________________ LinuxPLC mailing list [email protected]

Johan Bengtsson

I don't think that would be a problem either: The PLC program should be considered data, not code in this particular application, just because the program is GPL doesn't mean the data is (that is clearly stated in the licence). Even if the program does compile code the compiled code is considered data (look at the license for gcc it covers that up quite well I think) some few of the libraries might have better to be LGPL perhaps, but just only the basic things if anything. However, you can always make exceptions to the license saying that this or that is allowed, in particular that any PLC program is considered data, or at least is not affected by the GPL. I think someone else have to put that into words, after all my native language isn't even english so I am not the one to do it. /Johan Bengtsson ---------------------------------------- P&L, Innovation in training Box 252, S-281 23 H{ssleholm SWEDEN Tel: +46 451 49 460, Fax: +46 451 89 833 E-mail: [email protected] Internet: ---------------------------------------- _______________________________________________ LinuxPLC mailing list [email protected]

Marcelo Elias Del Valle

On Tue, May 08, 2001 at 09:32:54AM -0500, Juan Carlos Orozco wrote:
> programs. Siemens PLC (I don't know about the other brands) for example
> recognize this need and has the option to protect the code that runs on the
> PLC using passwords. My question is, because of the GPL license of LPLC the

Does anyone know if Siemens protocols like profibus (a modification of fieldbus, as I know), MPI and PPI (is it from siemens) are open? I would like to do drivers to these, but I didn't found any information about the possibility of do it on siemens site. Even the hardware protocol are
proprietary. A few PLCs can comunicate using ethernet, but most of them use proprietary protocols like siemens boards do. The only board I know a linux driver is Applicon...
How can we use linux on the PLC world this way? Is there a linux driver petition for PLCs?



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Curt Wuollet

Hi Marcelo

I have asked Modicon to grant us permission to use Modbus/TCP in a manner consistant with the GPL nature of the project. We will start by asking
certainly. The other groups can be asked publicly also. It is best if we can proceed that way. We can also reverse engineer some protocols or
implement from published data. I am not a lawyer and I don't know for certain where that puts us legally. In some cases we may have to just hack the protos for the public good. Some can be done with the various boards that talk devicenet, profibus, etc. This route is extremely expensive but should be relatively easy. The most good for the public would be if we wrote the protocols for the basic transport cards, for example get a CAN card and write DeviceNet software for it. Unless the proprietary vendors relent and help us out, it's gonna be real slow. I would think they would rather work with us so they retain the control
that's so important to them. Breaking down the Tower of Babel is a noble cause in itself that would help the industry immeasurably. They are all
in stand off mode where nobody dares to move first. I would like for our project to be a catalyst and a face saving way for them to open up in a controlled way with a level playing field. They would probably like for me to jump off a bridge somewhere. That leaves us the maximum room for negotiation and compromise.



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