Example: A programmer produces a library. They release that library under the LGPL and provide full source code.
The programmer wants to monetize their product as well.
Rather than offering a "pro" or "plus" version with extra features, the author writes a statement stating: "The LGPL licensed library is free for any use up to 100 operations per hour. If you need to use the library to do more than 100 operations per hour. please purchase a license." The author then offers a paid license that "allows" you to use the library for unlimited operations. They do this under the claim of a dual-license model. The author naturally knows some people will just bypass the limit, but expects that nobody in a serious business or commercial context would "violate" his license and would thus pay the fee.
These operations do not depend on any external server. There is no other technical enforcement of the limitation, other than that the LGPL code does a simple shifting counter to enforce a per-hour limit. But since the code is open source any developer could easily edit out that check.
Is this type of licensing compatible with LGPL licensing? I.e. if a commercial developer did just modify the library to remove that check, and then used the library beyond this 100-operation limit, would you be liable from a licensing standpoint?
If trademark or naming were the issue, suppose you just cloned the code, removed the check, rebranded the project and re-released it yourself under the LGPL with no limitations. Would this be a violation?
Put more succinctly: Can the author of an LGPL library prescribe written limitations on how the library is used, and legally, enforcibly demand payment for the same library with the only difference being you have the "right" to use that library in some other way?