There has been plenty of community mods for Thief, like it has for other Dark engine games. I expect Nightdive will use many of those community mods in their Thief game too, just like they did in System Shock 2 Remaster. Nightdive did not pay the modders, but the modders gave them permission to use their work for free. The difference here, of course, is that Nightdive games come with tech support from Nightdive (and Steam, and whichever stores that sell them). Players who find mods too complicated to install and maintain will benefit too.