The reason for having two sites in the first place was to separate the open source project from the commercial organization. In practise the same people controlled both sides. It felt like a Potemkin village https://en.wikipedia.org/wiki/Potemkin_village
We realized that it doesn't help to present yourself as an independent project when you are not. What matters is that the commercial organization is a good steward of the open source project. So we detailed how we want to do that https://about.gitlab.com/about/#stewardship and instituted a core team https://about.gitlab.com/core-team/
At times situations will come up that will allow you to show your true colors. For us it was the VLC people asking to open source a feature on HN and our competitor Perforce adopting GitLab. How you handle those situations is far more important than having multiple domain names.
I recommend that you consolidate everything under one website but you open up your company. See https://about.gitlab.com/handbook/ for inspiration.
Haha, you just made me realize that "The City and the City" by China Miéville could be used as a metaphor for such artificially divided organizations like the one you had (and many have - for better or worse reasons).
 http://amzn.to/29MWd3v [amazon affiliate link - just an experiment]
https://www.amazon.com/City-China-Mi-ville-ebook/dp/B003E2UQ... [Non-affilate link - to be a little more courteous ;-) ]