Deleting it from the modules directory and restarting will work. The proper way to remove a module is to mark it for deletion on the modules page and then restart Mango. That way if there is any uninstall work in the module it can know to do it.

:/opt/mango/web/modules $ ls
asciiFile dataFile graphicalViews mangoNoSqlDatabase pointLinks sqlds TCPIP BACnet dataImport http modbus reports ssh twilio
controlcore dataPointDetailsView internal onewire scheduledEvents sstGlobalScripts watchlists crowd dglux m2m2.license.xml persistent scripting sstGraphics zwave
dashboards excelReports mangoApi pid sqlConsole sstTheme

I don't have a license to MangoNoSQL module and do not anticipate using it at this time. I get the following line during startup:
/opt/mango/bin $ WARN 2017-08-08 10:07:59,993 (com.serotonin.m2m2.module.license.TimedLicenseEnforcementChecker.run:71) - mangoNoSqlDatabase is unlicensed, system will shutdown at Aug 08 2017 18:06:59

Rebooted Mango: Meta Data Source now appears properly and (as expected) shows up in the Modules directory.

I'm running on a RPi - and have several running successfully (with Meta) running 2.7.10. Meta was included in the 2.7.10 download.

Should I just delete it from the Modules directory (and reboot)? (The NoSQL module downloaded without my prompting or selecting as part of Core 2.8.8.)

Looks like I'm running properly now.

You can download it here: https://store.infiniteautomation.com/module/meta and place the zip into your Mango/web/modules directory, then restart Mango. It's very strange that it would not be installed and would not offer an update or installation. Can you tell me if there already is a Mango/web/modules/meta directory? What's in it?

The event is somewhat self explanatory. If the device is an ES or you feel you do have a license on that instance for the MangoNoSQL module, you can send in your GUID and we'll have a look.