Darklang for F# Developers

I find the license terms somewhat ambiguous. From the repo LICENSE.md

> Dark grants to the individual or entity agreeing to these terms (“you”) a license to use and modify the software, only for the purpose of creating and contributing improvements, bug fixes or other changes of the software (“Contributions”) to Dark. Contributions are voluntary. If you provide a Contribution to Dark, you must first agree to the current contribution license terms for the software.

It says it can be used and modified, but unclear if a modified version can be used 'in production', as that isn't purely for improvements/contributions. Any software that doesn't get real-world use is less likely to uncover many edge/corner cases.

Can the gist/motivation of this explained in a non-binding description? Though described as 'source available', it sounds like typical open/libre-source with the exclusion of forking.