MS_VBA_OPEN_IN_MEMORY applies equally to both MicroStation V8 and CONNECT editions.
In a Windows networked environment Windows EULA licensing restricts/limits the number of concurrent connections of file/folder shares to 20 Users/Devices. Similarly Microsoft IStorage limitations "Concurrent roots opened" have to abide by this restriction too. If a given organization requires more than 20 concurrent connections Microsoft client access licenses (CALs) can be purchased.
Early in MicroStation V8's release users reported these types of "scalability" issues and realized an option existed to open an IStorage container completely in memory and MS_VBA_OPEN_IN_MEMORY was then made available with the following options - hopefully more concise and easier to read below.
Not Defined (MS_VBA_OPEN_IN_MEMORY=NONE). Opens project from disk shared as read/write.
MS_VBA_OPEN_IN_MEMORY=ALL. Opens project in memory as read-only.
MS_VBA_OPEN_IN_MEMORY=READONLY. Opens project in memory as read and Edit.