Add open-source license picker

As discussed at the software license workshop on October 4th 2024, the tool:

• Should be pointed at together with the form
• Disclaimer "not legal advice/do your homework"
• Header of the tool: collaboration and societal impact.

Questions to be asked by the tool:

• External code/dependencies (legal obligations)
• Ecosystem/community preference

License possibilities: a few (look at Fluckiger). Recommended options:

• Strongly reciprocal: GPLv3 or later
• Permissive: Apache 2
• Weakly-reciprocal (TBD)
• GPL2/Apache 2: point to our recommendation (TBD)