While I highly doubt that, GitLab is Open Source - Github is not Open Source.
It's only partially open source. They let you smell the freedom, but you can't really have it.
I disagree; you can ignore the proprietary parts just fine.
For how long?
I don't know. So what? No different than a fully open source project that might be abandoned by its core developers. Either we fork or we move to another solution.
EDIT: It's not exactly an uncommon model; e.g. Nginx follows the same.
Complete and utter FUD, this is not the way GitLab operates - more importantly they are from the core an open source and transparent organisation that values both equally.
Yeah Yeah FUD you say... the same company that killed Gitorious.
You can self-host Gitlab easily (I manage two fairly big instances, with hundreds of users).