Realistically that takes a lot less than a fulltime engineer to support.
Of course this assumes no other value is acquired from the license, but if we take the comment at face value it seems worthwhile to just add it yourself.
It is good for society as a whole if people release their work publicly/open source. People will only release their work publicly/open source if it doesn't substantially hurt their potential earnings. So it's best to avoid taking advantage of publicly released work in ways that hurts their earnings (all else being equal).
Profit should go to the person who did the work making something. In this case gitlab did the work, and the person adding ldap here is almost entirely freeloading off of their work to make a profit. That isn't fair - especially when the freeloader has a direct negative impact on gitlab's earnings.
The person adding ldap support is not doing useful work for society, rather they are just doing busy work to redirect a stream of money towards them, that's not good.
And to add to all of these - the person doing this work is a competent engineer. They have lots of other ways to make money that are perfectly ethical, they do not need to resort to this.
I see opensource project that is missing usefull features and users who need them.
Why is "redirecting stream of money" towards me bad? Maybe I run orphanage and can use money more ethically...
That's a big part of the issue. It's not per engineer, as they don't allow mixing subscription levels.
So it's per everyone that needs some access.
So, no, this was absolutely productive. This isn't a particularly hard problem to solve.
ldap integration sounds pretty simple though, so maybe not in this case
Building custom in house tooling always costs 5x more than engineers believe, and ultimately doesn't improve your end product. This kind of tooling would probably require at least 100 engineers to justify the innate cost of building and maintaining it.