The OpenScience License include all the LGPL with the additional following condition:
If you publicly release any scientific claims or data that were supported or generated by the Program or a modification thereof, in whole or in part, you will release any modifications you made to the Program. This License will be in effect for the modified program.
A text version of the license is available here.
The OpenScience License ensure that scientific code that is released as open-source software shall remain open-source in the event of the publication of new, derivative work by another researcher based on the software.
Scientific publication is not an object code of the software that generated it. As such, it does not benefit for the derivative work protection of the LGPL.
Open-sourcing code that generated scientific claims is crucial to ensure proper reproduction and verification of the results. The OpenScience license aims to encourage the open-sourcing of scientific code by ensuring its authors that they will benefit of further modifications made to their code.
Why the LGPL ?
Scientific experiments are many and diverse, and often bring various technologies together. The LGPL ensures that the released code can be used in environments where releasing everything open-source is simply not possible.