Let's say there's a piece of OSS that I think meshes well with a business idea I'm working on. What are the best practices here?
I'm going the indie hacker route, so very limited resources at the beginning.
Do you want to use OSS software? Great, go ahead! The license isn't going to get in your way, it's essentially free-as-in-beer for you.
Do you want to make changes to the software and redistribute it? You may need to do so under the original license (for GPL and similar).
This is called "under-capitalization" and is a fundamental business problem.
The best practice is adequate capitalization.
Adequate capitalization lets you focus on customers, revenue, and cashflow...aka "the things that matter" instead of chasing your tail with free software.
Or to put it another way, the best practice is obtaining money because obtaining money is what businesses do.
Good luck.