body: I am tasked with making a due diligence of legacy software. Part of this is to reassess all software dependencies and their licensing. However, there are various ambiguities, occurring most commonly in old code.
  
  
  I am now facing this particular issue:
  I have a dependency that I have seen to be indicated in the code to be licensed under `L-GPL`. With a fair amount of certainty this can be identified as the [GNU Lesser GPL](https://en.wikipedia.org/wiki/GNU_Lesser_General_Public_License). However, I cannot find information about the version this refers to.
  
  
  My question is what version should I assume, and I can think of several options:
  
  
  1. The version of the time of creation of the software, namely [LGPL 2.1](https://www.gnu.org/licenses/old-licenses/lgpl-2.1.html), or
  2. The version of the time of our use of the software, which practically would allow me to choose today's most recent version, i.e. [LGPL 3.0](https://www.gnu.org/licenses/lgpl-3.0.en.html).
  
  
  To my understanding the difference between the two is negligible, but the combination of legal and technical context urges me to try to be specific as much as possible.
  
  
  Please, excuse me if this question has already been asked in some other form and I haven't been able to identify it with my searches.
  
  
  
title: License ambiguity - When license version is not specified by author?