RhodeCode have the most advanced Permission system on the market, allowing things like permission inheritance, permission delegation. All comes in a format that doesn't get hard to manage at scale.
RhodeCode CE (Community Edition ) is free and open source. Enterprise Edition (EE) adds premium support, corporate authentication. and tool integrations on top of the RhodeCode CE.
It's open source and it can be installed on your own machine, which gives high security and isolated environment for the codes. Whole application installation is super easy and independent from the Linux distribution.