OnSSI bought Seetec in 2015. OnSSI uses Seetec's 'engine' / 'VMS' / 'recorder' in their VMS. Seetec still sells / uses their own front end for their own customers.
OnSSI is North America focused, Seetec is European focused.
I've asked OnSSI to comment on this.
OnSSI feedback on contrast:
[OnSSI] Ocularis is an enterprise VMS and PSIM that focuses primarily on tactical operations and advanced alerting. [Seetec] Cayuga is also an enterprise VMS with more of a focus on business processes. Additionally, there are some feature sets and technology partner integrations that are unique to each product based upon local market requirements. There is also significant market segmentation, as Ocularis and Cayuga are not typically available in the same local markets.
OnSSI on migrating to Seetec engine and more migration tools in 5.2:
Equally as important, incorporating the See Tec recording engine has provided many advantages and new features for Ocularis users including full encryption, higher security for the recorded video database, direct recording to a NAS, the ability to use lower cost SATA hard drives and Manufacturer specific Smart Camera Drivers. These Smart Drivers allow customers to use newly released cameras, right out of the box, for most major manufacturers without waiting for driver pack releases. Ocularis 5.2, being released shortly, will also have new tools to make migration much simpler and faster.