I've been asked this question on numerous occassions. Here is my take on why it has happened.
1) Sabre Airline Solutions invested significantly in a set of standard core technology platforms built on open source technology (Java Swing, JSP/Struts, JDO, Hibernate, Spring, J2EE technologies, etc.). This rich experience with open source has created a desire among those involved to share back with the community.
2) During this investment phase a number of open-source friendly folks were hired and moved into influential positions
3) We understood that whatever innovations we had arrived at, others were probably at the same stage or would shortly be there. Why not put our stuff out and let it be a part of the early wave (for Ajax & rich internet applications) and perhaps influence how things shape up in the world. of the web Sabre has a history of innovations and so it fit with this thinking.
4) We understand that we are not really in the business of building frameworks. If we get our frameworks out to the larger community then they will only get better.
5) Those of us involved are pretty passionate folks that really get excited about innovation!
6) We have the right people at executive level that are willing to think outside the box about our how some of our software gets developed.
7) Its just great publicity.
I have been extremely pleased during my last three years at Sabre. I have had tremendous support in every endeavor I have launched. This support has been at the executive level, at the product marketing level and at the development level. I think things were just ripe for Sabre to do something like this.
Anyway that's my view on it.