A Paid Course Counts as Commercial Use
Using a source that's free for personal enjoyment inside a course you're selling is treated as commercial use, which is a different category with different rules than personal use. Copyright problems are much harder to undo once a course has already gone on sale, so building the habit of checking a source's license terms at the moment you download it β not after you've already published β is the safer approach. This is general information, not legal advice; consult a legal professional for a specific situation.
Where to Look for Sources You Can Actually Sell With
Rather than searching generically and hoping a source is safe, look specifically for stock libraries, font foundries, and music services that explicitly advertise a commercial-use or extended license tier, and keep a simple record of where each asset came from and what license it was under. That record becomes valuable if a licensing question ever comes up after the course is already live.
Frequently Asked Questions
If I credit the source, can I use any image I want?
No β some licenses require attribution as a condition of use, but others prohibit commercial use entirely regardless of attribution, so you need to confirm commercial-use permission separately from whether attribution is required.
What should I do if I realize later that I used something without proper rights?
Replace or remove the source as soon as you notice the problem, and if needed, reach out to the rights holder to request retroactive permission β acting quickly tends to prevent a small oversight from turning into a bigger problem.