Hi, Does the open source version have any user limit similar to the commercial version? We bought an education license from MT few years ago with 35 editors limit. We are currently thinking about extending this. What are our options? Can you just upgrade everything to the open source version? Is customer support only service that is not part of the open source licensing?
I would appreciate some feebback.

MTOS has no user/blog/etc limits. Go nuts.
In terms of services yes official support is the main thing you'd lose. But MTOS also doesn't include the Professional Pack. If you already have the pack I don't suppose there's anything to stop you from continuing to use it, but you wouldn't be entitled to any future free upgrades beyond the period covered by your existing license.