Licensing consideration with extract-msg dependency

[luchaf]

Hi @fleetingbytes,

First, thank you once again for your helpfulness with the licensing clarification in issue #46. Your quick response and willingness to update the LICENSE file was really appreciated.

I wanted to bring up another licensing-related topic I stumbled upon while working with rtfparse. I noticed that the extract-msg library that rtfparse depends on is licensed under GPL3, which creates a licensing compatibility challenge. When GPL3 code is included as a dependency, it effectively requires any distributed software containing it to comply with GPL3 terms, which conflicts with the MIT license's permissive nature.

Looking at the codebase, I see that extract-msg is used specifically for handling MSG files in the CLI, which appears to be separate from the core RTF parsing functionality that makes rtfparse so valuable.
Would you be willing to consider removing the extract-msg dependency to maintain clear MIT licensing throughout the project?

This would:

• Ensure rtfparse remains fully MIT-licensed without any GPL3 restrictions
• Simplify the dependency tree
• Keep the library focused on its core strength of RTF parsing
• Make it easier for organizations to adopt rtfparse without licensing concerns

I understand that MSG support might be useful for some workflows, but users who need to process MSG files could use extract-msg directly for that specific use case, while rtfparse could focus on being the best RTF parsing solution.

I really appreciate rtfparse and the work you've put into it. This licensing clarity would help ensure more organizations can confidently use your excellent RTF parsing library.

Would you be open to this change? I'd be happy to submit a PR removing the MSG-related functionality if that would be helpful.
Thank you for considering this!

[fleetingbytes]

Thank you for bringing this up. This licensing problem was a negligence on my part. I forgot to look up the licensing sheme of the extract-msg dependency in included. I want to use a non-aggressive license. This will take a while to correct. I will be unavailable for the next two weeks, but will attend to this issue.

@luchaf Please open a PR if you have the time to work on this. That would be a great help! I can only spend an hour or so per week maintaining this so your PR would greatly accelerate this. Please update also the CLI usage examples in the readme. extract-msg should be an optional dependency. I'm not sure if that package provides a cli, but if so, add some example CLI commands to extract the RTF from an Outlook .msg file. This will be a compressed RTF, so our CLI must still run the compressed_rtf (MIT-licensed) to decompress the RTF before parsing it.