Unfortunate if I came off that way, that was not my intention. Just tried to keep things short by bundling all the 3 mentioned engines into "different brands of free".
UE4 is indeed open source, though not open to the extent of your average open source project, YET. But I'm not at all trying to give them a hard time about it. I know these things have to happen gradually. What they're doing is great.
I think smaller frameworks like jME, LibGDX, Cocos-* will still live quite a while, exactly because of the community and contributors momentum the bigger engines lack.
BTW, I wanted to have a look at the jME source and noticed that the website misses a GH link, you should definitely put it up there.
UE4 is indeed open source, though not open to the extent of your average open source project, YET. But I'm not at all trying to give them a hard time about it. I know these things have to happen gradually. What they're doing is great.