Were they actively making changes to the project and running custom builds? If not then they just had nothing to contribute to the project and there is certainly nothing to feel disgusted about.
Even if they were making local changes, I personally couldn't fault them, really; they're playing by the rules.
If they want to give up the intangible benefits they would get from sharing those changes (at least the non-business-strategic ones), that's disheartening, but I wouldn't lose any sleep over it.
If they want to give up the intangible benefits they would get from sharing those changes (at least the non-business-strategic ones), that's disheartening, but I wouldn't lose any sleep over it.