I use to work for CommVault, but not in touch with the software for some time now. However, I am pretty sure you should be able to use use block-level backups (for OSDP clients) with your IntelliSnap Controller based license. To be honest, OSDP (In NetApp terms - OSSV [Open System SnapVault]) was created to backup data from non-NetApp hardware. I guess, even with OSDP it did block-level Incrementals (using native snapshot engine). You should be good as long as the configuration is met as per the documentation of CommVault.
IntelliSnap can be used with : NetApp (or any other compatible arrray) as well as non-netapp Hardware: NetApp Hardware (data is residing on volume presented from NetApp) - NetApp Hardware Snapshot engine. Non-NetApp Hardware (data residing on partitions that are not provisioned from NetApp) - CommVault uses native snapshot engine, for example on windows , it can use vss to create the snapshot for non-netapp hadware. Similarly for Linux, I guess the requirement for native snap is that the file systems must reside on top of LVM.
REACH OUT TO CommVault Forum: (if you don't hear any further here)
CommVault forums can be useful for any queries related to commvault/snapprotect. You can try posting your query here.