Is it allowed to copy code from existing WordPress plugins to build own plugins?

Server & Coding ForumIs it allowed to copy code from existing WordPress plugins to build own plugins?
willisupportz asked 4 months ago PPU : 5

I would like to copy code from existing WordPress plugins to create my own plugins. Is this allowed? In general it should be allowed to copy Open Source software. But I wonder how the plugins of WordPress are licensed becasue some of them come as paid pro plugins integrated into an Open Source WordPress system. Can anybody help me here?