What I've heard from those I've talked to who have open sourced things successfully, they always talk about open sourcing things that work like plumbing or are

What I've heard from those I've talked to who have open sourced things successfully, they always talk about open sourcing things that work like plumbing or are foundational to what you do, but keeping the core of what you do yours. I feel a similar inclination toward premade solutions, if something is the very core of your business or is the primary differentiator of your business then building a custom solution or creating an internal department is appropriate, if it isn't then buying a solution or using other people's software is usually the better choice.