Generally, lawsuits arise under two conditions:
- You start making lots of money.
- You're doing something that causes someone else to lose lots of money.
The same is true of software licenses. You won't get sued for hobby projects with low impact. But if you start making money, others will want a piece. If you start impeding on someone else's revenue, they will want to protect it. If you're in either of these situations, software licenses matter.