That’s sort of what the phrase has started to mean because of how it’s used by many American police officers. It has more reasonable historic meanings.
The "historic" meaning directly references a military regiment standing their ground against the enemy (see "thin red line"). This particular quote has always evinced a highly adversarial attitude.
So? The problem with the police using it for its historic meaning is that they are ostensibly not a military force but they act like one; using the phrase makes it almost explicit. Why is it bad if these open source maintainers use it, presuming they meant this “hold the battle line” meaning?
It probably wouldn't be bad (or at least as bad) if they used the original which isn't tied to the politics of policing. The “thin red line” inspired the “thin blue line”, but they are distinct sayings with different denotation and connotation.
Not that it is incorrect to say that the phrase is tied to policing, just that it is similarly not-incorrect to say it is not tied to policing. It is context-dependent. It’s not so obvious that this particular use of that phrase is at all related to police work.