Hi,

I'm currently in the process of writing a little application as a side-project in my own time. Once it's at a stage that's suitable to release I planned to release it under some form of open source license. The thing is that I have some pre-existing custom libraries (dynamically linked to the app) that have been released with other non-GPLed apps I've written and I don't want to GLP/LGPL it/them as well.

I've tried searching Google and these forums, but I seem to be in a backward situation to what everyone else asks about. Rather than an LGPL library and a 'proprietary' (non-licensed) app, I've got a non-licensed library and a hopefully open sourced app that I want to distribute together.

My reading of the LGPL (and what I've picked up from some FAQs and history) is that it was the Library GPL but is now the Lesser GPL to help people realise it isn't just for libraries (or possibly that libraries aren't just for LGPL, I'm not sure). Unfortunately the wording still implies LGPLed library linked to by other app and not visa-versa.

The Creative Commons 'layman summary' and the Wikipedia page imply that LGPL works both ways with regards linking to non-LGPL or being linked from non-LGPL and so I'd be okay, but this old KDE post says (possibly incorrectly) that you can't link to a proprietary library from LGPL, which fits my reading of the current LGPL wording.

For added complication and confusion on my part, I'm writing it in C# (because I find it much quicker to develop in, it's what I'm used to, and my target audience are mainly Windows users - although I will, of course, be making it Mono/Linux compatible). If the LGPL stops LGPL apps using proprietary libraries (like GPL does) then surely I'd be unable to release a C# app in (L)GPL due to the fact that it requires MS's .Net framework (assuming we're talking a pre/no-Mono situation). I know there's an exception for core OS components and similar that the framework may fall under, but it still added extra legal situation confusion for me on top of the confusion of the license wording, especially when I plan to distribute my library as well as link in the same way as I would to, for example, System.Windows.Forms.

So, other than the ethical "it should all be GPL, because otherwise baby penguins cry" comments, can I release an LGPLed application that links to a 'proprietary' library and, more importantly, is distributed along with the library? And if not, what license choices do I have for the application?

Thanks

IBBoard

p.s. sorry if that lot is rambling or doesn't make sense. I think all of the legalese has driven me crazy!

IANAL, but I think doing this is in the clear. Annoying, yes, but not prevented by the license. To my undestanding, the big thing the (L)GPL says is that if Foo is licensed (L)GPL, then related program Bar must be as well. Using basic predicate logic, if Foo is not licensed (L)GPL, then the value of the consequent statement (Bar is licensed (L)GPL) does not matter, the whole statement is true.

Maybe I'll pose this to a Professor of mine (who is a lawyer, a computer geek, and an Open Source advocate).

That depends on what Foo is and whether you're talking GPL or LGPL.

If Foo is a library and Foo is LGPL then application Bar that uses Foo can be proprietary (to keep the library open source but also allow for its take-up in Industry).

If Foo is a library and Foo is GPL then any application Bar that uses it must also be GPL.

If Foo is an application and Foo is GPL then any library, Bar, that it uses must also be GPL (or possibly LGPL, I'm not sure) so that you cannot exploit a loop-hole in the GPL and slowly syphon functionality out to non-GPL'ed libraries and render the main code useless. That is explicitly stated for the GPL, but nothing is said for the LGPL (as it is designed for the inverse where the library is LGPL).

I understand those situations, it's just LGPL app and non-open source library that I don't. I know it's okay to dynamically link to core .Net libraries because the open source Mono implementation exists, otherwise all C# apps would be non-GPL'able, but it's distributing my additional preferences/translations with it that hits the legal questions. I could possibly distribute them separately and be okay, but I know that far too many users will email me instead of R'ingTFM and seeing that the error is because they don't have a required library (or an alternative implementation of it)