I am looking for suitable COTS GIS server product for Linux platform. The product should allow 500 Clients concurrently and should have Java / C++ development APIs. So far I found ESRI ArcGIS server which supports for Linux. I need few more products which have good performance like ESRI. Kindly share the list of available COTS (Commercial off the shelf) GIS server products.
These are my two favorite which run on linux. I believe they do meet your requirements.
Even though they are free, you can pay for support. "linux is free if your time is worthless" (for "free" as in cost - "free" as in freedom isn't about money...
There are also "products" built out of these, such as the OpenGeo Suite
ArcGIS Server (Linux) 10.1
ESRI has greatly improved it install process of ArcGIS Server on Linux
FME Server 2012/13 [Recommended]