GlassFish eventually became a killer application server, now it is just a great developer runtime:
"Oracle recommends that existing commercial Oracle GlassFish Server customers begin planning to move to Oracle WebLogic Server, which is a natural technical and license migration path forward"and
"Oracle will no longer release future major releases of Oracle GlassFish Server with commercial support – specifically Oracle GlassFish Server 4.x with commercial Java EE 7 support will not be released."but
"To summarize, Oracle is committed to the future of Java EE. Java EE 7 has been released and planning for Java EE 8 has begun. GlassFish Server Open Source Edition continues to be the strategic foundation for Java EE reference implementation going forward. And for developers, updates will be delivered as needed to continue to deliver a great developer experience for GlassFish Server Open Source Edition. We are planning for GlassFish Server Open Source Edition 5 as the foundation for the Java EE 8 reference implementation, as well as bundling GlassFish Server Open Source Edition 5 in a Java EE 8 SDK, which is the most popular distribution of GlassFish."
I was able to introduce GlassFish to many larger organizations just by mentioning the availability of commercial support. The mix of "Reference Implementation" and "Commercial Support" was a huge selling point. The only problem: only few customers knew about the availability of Oracle's commercial support offerings.
You could start with GF as developer environment then proceed to production having commercial support available. This was particularly interesting for smaller companies and start-ups.
I'm not sure whether it is reasonable to develop on GlassFish and deploy to WebLogic. I would always use the same runtime for both.
However this announcement and Oracle's "optimizations" is the perfect opportunity for other vendors like TomEE with commercial support by tomitribe, or wildfly with commercial support by redhat or the WebSphere liberty with support from ibm, to step in.
Also, there is room now for any company to offer commercial support for GlassFish (IBM, SAP, SalesForce or RedHat would be fun :-)). GlassFish is open source and provides interesting HA features, even rolling updates, session replication and cluster management. Many companies are running critical software on GlassFish... GlassFish comes even with pragmatic monitoring tool :-).
See you at Java EE Workshops at MUC Airport (we will cover migrations as well :-))!