Ask HN: Should you put your freelance experience on your resume if you work FT?

I’m wondering if or where it would be beneficial for a developer to mention freelance work they’ve done while working full-time. My understanding is that some employers own their employees’ IP, so how do they view a potential employee who regularly does freelance work outside of their 9-5? If the freelance work is related to your FT position, is it a net positive or negative?