My first response was of initial excitement. And then 30 seconds later… a big yawn. The Application Server market is mature and growing slowly (if at all). The big players like IBM and BEA have cornered the enterprise customers that are willing to pay for the software and support. For Red Hat this clearly makes sense as it can now sell more software to its customers while lowering the cost of delivery. In some sense the strategy is very similar to that of CA and other major acquiring companies to consolidate and squeeze out costs.
But this is not an earthshaking event and will have very little effect on the competitive landscape. The big software vendors were any way moving away from selling just the application server to selling higher software like BPM, Integration, Identity Management etc. If anything this purchase by a neutral vendor like RedHat helps Oracle and others that have bet big on Linux platform.
Now here is what can really change the game… RedHat acquires MySQL. Now that would be interesting.