Right to modify proprietary software linked to LGPLv2.1-licensed library?

Question

The LGPLv2.1 license states in Section 6:

6. As an exception to the Sections above, you may also combine or link a "work that uses the Library" with the Library to produce a work containing portions of the Library, and distribute that work under terms of your choice, provided that the terms permit modification of the work for the customer's own use and reverse engineering for debugging such modifications.

Let's assume here that the combined work, refers to a proprietary closed source software linked to a LGPLv2.1-licensed Library.

Does this mean that the user who receives a distribution of the combined work, must be able to modify the proprietary closed source software for his own use and reverse engineer it for debugging such modifications?

If yes, does this mean that the user must have the right to modify such proprietary closed source software for his own use (i.e. not distribute such modifications further), but the license does not require that the user should receive the source code to that proprietary closed source software?

Here, I assume that the bolded word "work" above refers to the "work that uses the Library" i.e. the proprietary closed source software in my example.

Answer 1

The way I read it is that "the work" refers to a "work containing portions of the Library", made by "combining or linking a "work that uses the Library" with the Library".

The way I understand that is that, if you choose to link your proprietary code to an LGPL library, and distribute the result, you may not contractually forbid reverse-engineering of this resulting work, nor may you forbid the recipient to alter or edit the resulting work. You don't have to make it easy (by providing sources, and freedom; that is reserved for works that include GPL-licensed libraries) but you can't require the recipient to forego the right to try.

Answer 2

The GPL license basically says: "There are things that the law didn't give you permission to do, but we give you permission to do them if you follow certain conditions". For example, you have the right to combine GPL licensed software with propriatery software and publish both under the GPL license - as far as the GPL license owner is concerned.

However, the proprietary software most likely has its own license that doesn't allow this. So distributing the combined software under GPL means you commit copyright infringement against the proprietary part. (I believe that means you never had the right to distribute under the GPL in the first place, so you didn't meet the conditions of GPL either, so you have copyright infringement against the GPL licensed code as well).

You MUST publish under the GPL license to avoid copyright infringement, but you CAN'T do this, so you cannot distribute the combined software since it means you would commit copyright infringement.

Now if you gave that software to me, and I read "GPL license" I would be tricked into believing it is GPL licensed. The GPL license means nothing if the provider didn't have the right to publish under that license. So I might use this software and be in huge legal trouble with everyone involved.