License related questions

[sunayana]

Hello,
We would like to use your FillSpillMerge library internally within our company, we notice that this should be fine since it has an MIT license. But since FillSpillMerge uses RichDEM which has a GPL-3.0 license we were wondering:

• whether FillSpillMerge should also have GPL-3.0 license and whether we are still fine using FillSpillMerge internally?
• or whether it would be possible to change the license of RichDEM to MIT

We would like to know your recommendations related to this.
Thank you very much.
Sunayana