"an open group of companies who run open source programs" who are seeking to "committed to working together in order to overcome" the challenges of using FOSS
If the megacorps want to get involved in the advancement of FOSS, they have an incredibly clear path to do so: Paid Development. They can fund it themselves, if they want to decide what gets built next. Or, to get a little creative, how about this: Put together some training materials for corporate legal departments explaining that companies can legally, safely, contribute code developed on company time back to FOSS projects. Put together a promotional campaign to convince corporate bean counters that contributing code back to FOSS is a worthwhile investement of company resources.
In short; help channel money into FOSS, either directly or by clearing the red tape that keeps us from creating and kicking back enhancements built for the benefit of our companies. Hey, maybe lobby congress for a tax write-off for code contributions to 501c3s.
Developers contribute to FOSS by giving of their greatest strength, development. If megacorps want to help, they should give of their greatest strengths; money and bureaucracy.
(and yes, I know, they think telling people what to do is their greatest strength, but they've got another think coming when it comes to telling FOSS developers what to do)