> Do you use webhooks on GitHub? That would actually be pretty easy to implement,
Bingo. Full implementation, in Bash: http://faq.sealedabstract.com/gitlab_mirror/
> What are you afraid of?
Mostly, that you'll get bought by the likes of Oracle. In spite of my quibbles about CE features, I think you're doing a (mostly) fine job of CE right now. But your acquirer will see CE as a cost center (there's no revenue) and will want to "streamline" by focusing on enterprise (where your balance sheet is). GitLab.com will also look like a cost center, and will either shut down, turn into a datamining opportunity, or go through the bad PR of no longer being free. I fully anticipate, in 5-10 years time, that I will be running a CE fork to get out from under your acquirer, just like StarOffice, MySQL, Hudson, etc.
Contrast with GitHub, who makes a silly amount of money from people like me. Their acquirer would be mad to screw up a winning formula.
The good news is, GitLab is such a good product that I still hugely prefer it even after "pricing in" the risk (cough, certainty) that my days are numbered. It is an amazing tool, it really shows that you care about it. For now.