Avoid GPL Dependencies as Hard Dependencies

Scirpy currently lists both igraph and python-Levenshtein as hard dependencies. Since these packages are licensed under the GPL, their inclusion could inadvertently impose GPL conditions on Scirpy, which is intended to be BSD licensed.

Potential Impact:

• License Conflict: Incorporating GPL components as mandatory dependencies may force Scirpy to adhere to GPL terms, conflicting with its BSD licensing.
• Distribution Concerns: This could lead to legal and distribution complications, undermining the intended permissive licensing model of Scirpy.

Proposed Solutions:

• Make Dependencies Optional: Consider making igraph and python-Levenshtein optional dependencies to avoid enforcing GPL licensing on the entire package.
• Explore Alternatives: Investigate alternative libraries that provide similar functionality but are licensed under more permissive licenses (e.g., MIT or BSD).

I believe addressing this will help maintain Scirpy's intended BSD license and prevent potential licensing issues. Happy to discuss further or help test any changes proposed.

Start by locating Scirpy's dependency declarations and the uses of igraph and python-Levenshtein. Compare making them optional with replacing them, then check packaging metadata and relevant tests; done means the chosen approach avoids hard GPL dependencies without breaking supported functionality.