Well, basically, if you don’t need commercial support.
At ESUG, the GemStone/S team announced that the free web edition of GemStone/S has had its limits raised. Maximum repository size is now 16GB (up from 4), shared page cache is 2GB (up from 1), CPU limit is 2 (up from 1), and the limit on the total number of objects in the repository has been eliminated. So if it was possible to fit ‘em in 16GB, you could keep track of 2^40 objects (approx. 1 trillion).
You can upgrade an existing GLASS installation using the updated key files available here.
It boggles my mind that this sort of technology is available for free. Our projects are almost exclusively GLASS-based now, and all of them are running well within the limits of the new free license. Performance is great, customers are happy, and our developers love it. Kudos to GemStone for a great product!