How big is FreeRADIUS?

I can't tell for sure, but there are a lot of people using FreeRADIUS. The main FreeRADIUS page says it's in the “top 5″ servers, but that's really a guess based on the following information:

RADIUS Server Software

Maybe the main web page needs updating. I can't think of other RADIUS servers that have as big a market share as the four listed above. And many commercial RADIUS products not listed above use FreeRADIUS as the protocol engine for their product.

In terms of cusomer base, I know of at least 4 deployments with 2 to 8 million users. I know of hundreds of small sites (universities, etc) with tens of thousands of users. Most sites won't let their names be used publicly (for a number of reasons), but if you're planning on deploying FreeRADIUS, you're not alone.

So FreeRADIUS looks to have a significant portion of the RADIUS server market. Without doing more detailed analysis, the best guess is that somewhere between 10% and 50% of RADIUS server installations world-wide are for FreeRADIUS. And with 802.1x deployments becoming ubiquitous, there are likely many, many more people installing FreeRADIUS in home networks with less than 10 users.

That's not bad for a software product with no support staff, no development budget, and no marketing.