Consider making the software license part of the dependency

[eric-nieuwland]

Currently, the software dependencies first are first split into 'dependsOn/open' and 'dependsOn/proprietary' lists before being defined.
No further details to the nature of the license can be specified.

The suggestion here is to merge 'dependsOn/open' and 'dependsOn/proprietary' into 'dependsOn/software', while adding 'license' to the definition of 'dependency'. This will allow to use 'open' or 'proprietary' as value for 'license', but also a SPDX license expression (see https://spdx.org/licenses/) or simply 'commercial'.